Ad orientem is a "Latin phrase meaning "to the east" and is used in many contexts. In the "Vulgate, which is the "Catholic Church's official Latin translation of the "Bible, it appears 36 times, with varied contexts. However, in the contexts both of "Christian prayer and of "Christian liturgy it is employed with specific meanings that will be examined in this article.
The earliest known use of the exact Latin phrase ad orientem to describe the "Christian practice of facing east when praying is in "Augustine's De Sermone Domini in Monte, probably of AD 393. The equivalent Latin phrase, ad orientis regionem (to the region of the east), was used two centuries earlier by "Tertullian in his "Apologeticus (AD 197) to indicate the practice.
"Clement of Alexandria ( c. 150 – c. 215) says: "Since the dawn is an image of the day of birth, and from that point the light which has shone forth at first from the darkness increases, there has also dawned on those involved in darkness a day of the knowledge of truth. In correspondence with the manner of the sun's rising, prayers are made looking towards the sunrise in the east."
"Origen (c. 185 – 253) says: "The fact that [...] of all the quarters of the heavens, the east is the only direction we turn to when we pour out prayer, the reasons for this, I think, are not easily discovered by anyone."
In 1971, Georg Kretschmar proposed a connection between the Christian custom of praying towards the east and a practice of the earliest Christians in Jerusalem of praying towards the "Mount of Olives, situated to the east of the city and seen as the locus of key eschatological events and of the "Second Coming of Christ. In this view, the localization of the Second Coming on the Mount of Olives was abandoned after the "destruction of Jerusalem in AD 70 and the eastward direction of Christian prayer became general. The theory of Christian prayer towards the Mount of Olives has been rejected by Stefan Heid, but is defended by Uwe Michael Lang. On the other hand, Lang says that it was at that time a practice even among many Jews to pray eastward.
Paul F. Bradshaw says that the Christians adopted the eastward orientation when praying, as did the Jewish sects of the "Essenes and the "Therapeutae, for whom "the eastward prayer had acquired an "eschatological dimension, the 'fine bright day' for which the Therapeutae prayed being apparently the "messianic age and the Essene prayer towards the sun 'as though beseeching him to rise' being a petition for the coming of the priestly Messiah."
The "primitive Church had no knowledge of the origin of the practice. Origen says: "The reasons for this, I think, are not easily discovered by anyone." Although the general custom among Jews was to pray towards the temple in Jerusalem, Clement of Alexandria, Origen's older contemporary, says that the custom of praying eastward was general even among non-Christians: "In correspondence with the manner of the sun's rising, prayers are made looking towards the sunrise in the east. Whence also the most ancient temples looked towards the west, that people might be taught to turn to the east when facing the images."
It is not without reason or by chance that we worship towards the East. But seeing that we are composed of a visible and an invisible nature, that is to say, of a nature partly of spirit and partly of sense, we render also a twofold worship to the Creator; just as we sing both with our spirit and our bodily lips, and are baptized with both water and Spirit, and are united with the Lord in a twofold manner, being sharers in the Mysteries and in the grace of the Spirit. Since, therefore, God is spiritual light, and Christ is called in the Scriptures Sun of Righteousness and Dayspring, the East is the direction that must be assigned to His worship. For everything good must be assigned to Him from Whom every good thing arises. Indeed the divine David also says, Sing unto God, ye kingdoms of the earth: O sing praises unto the Lord: to Him that rideth upon the Heavens of heavens towards the East. Moreover the Scripture also says, And God planted a garden eastward in Eden; and there He put the man whom He had formed: and when he had transgressed His command He expelled him and made him to dwell over against the delights of Paradise, which clearly is the West. So, then, we worship God seeking and striving after our old fatherland. Moreover the tent of Moses had its veil and mercy seat towards the East. Also the tribe of Judah as the most precious pitched their camp on the East. Also in the celebrated temple of Solomon, the Gate of the Lord was placed eastward. Moreover Christ, when He hung on the Cross, had His face turned towards the West, and so we worship, striving after Him. And when He was received again into Heaven He was borne towards the East, and thus His apostles worship Him, and thus He will come again in the way in which they beheld Him going towards Heaven; as the Lord Himself said, As the lightning cometh out of the East and shineth even unto the West, so also shall the coming of the Son of Man be. So, then, in expectation of His coming we worship towards the East. But this tradition of the apostles is unwritten. For much that has been handed down to us by tradition is unwritten.
He [Christ] has taught us all the economy of the Christian religion: baptism, laws, ordinances, prayers, worship in the direction of the east, and the sacrifice that we offer. All these things He practiced in His person and taught us to practise ourselves.
Outside of Rome, it was an ancient custom for most churches to be built with the entrance at the west end and for priest and people to face eastward to the place of the rising sun.
On the history of the custom of constructing many but not all churches in this way, see "Orientation of churches.
It is common for members of "Oriental Orthodox Churches to pray privately in their homes facing eastward; when a priest visits one's home, he usually asks where the east is before he leads a family in prayer.
On the other hand, there are some small Christian groups that consider praying towards the east "an abomination".
As a Google search shows, the phrase ad orientem is today much more commonly used to describe a particular orientation of a priest in "Christian liturgy, facing the apse or wall behind the altar, with priest and people looking in the same direction, as opposed to the "versus populum orientation, in which the priest faces the congregation. In this use, the phrase is not necessarily related to the geographical direction in which the priest is looking and is employed even if he is not facing to the east or even has his back to the east.
This usage, by which ad orientem is opposed to versus populum, is recent. The "Tridentine "Roman Missal, the last edition of which was published in 1962, says: "Si altare sit ad orientem, versus populum, celebrans versa facie ad populum, non vertit humeros ad altare, cum dicturus est Dóminus vobiscum, Oráte, fratres, Ite, missa est, vel daturus benedictionem ..." (If the altar is ad orientem, towards the people, the celebrant, facing the people, does not turn his back to the altar when about to say "Dominus vobiscum ["The Lord be with you"], "Orate, fratres [the introduction to the prayer over the offerings of bread and wine], and "Ite, missa est [the dismissal at the conclusion of the Mass], or about to give the blessing ...)
In early Christianity, the practice of praying towards the east did not result in uniformity in the "orientation of the buildings in which Christians worshipped and did not mean that the priest necessarily faced away from the congregation, the meaning today commonly attached to the phrase ad orientem. The earliest churches in Rome had a façade to the east and an apse with the altar to the west; the priest celebrating Mass stood behind the altar, facing east and so towards the people. According to "Louis Bouyer, not only the priest but also the congregation faced east at prayer, a view strongly criticized on the grounds of the unlikelihood that, in churches where the altar was to the west, they would turn their backs on the altar (and the priest) at the celebration of the Eucharist. The view prevails therefore that the priest, facing east, would celebrate ad populum in some churches, in others not, in accordance with the churches' architecture.
It was in the 8th or 9th century that the position whereby the priest faced the apse, not the people, when celebrating Mass was adopted in the basilicas of Rome. This usage was introduced from the "Frankish Empire and later became almost universal in the West. However, the "Tridentine "Roman Missal continued to recognize the possibility of celebrating Mass ""versus populum" (facing the people), and in several churches in Rome, it was physically impossible, even before the twentieth-century liturgical reforms, for the priest to celebrate Mass facing away from the people, because of the presence, immediately in front of the altar, of the "confession" ("Latin: confessio), an area sunk below floor level to enable people to come close to the tomb of the saint buried beneath the altar.
Anglican Bishop "Colin Buchanan writes that there "is reason to think that in the first millennium of the church in Western Europe, the president of the eucharist regularly faced across the eucharistic table toward the ecclesiastical west. Somewhere between the 10th and 12th centuries, a change occurred in which the table itself was moved to be fixed against the east wall, and the president stood before it, facing east, with his back to the people." This change, according to Buchanan, "was possibly precipitated by the coming of tabernacles for reservation, which were ideally both to occupy a central position and also to be fixed to the east wall without the president turning his back to them."
In 7th century "England, it is said, Catholic churches were built so that on the very feast day of the saint in whose honor they were named, Mass could be offered on an altar while directly facing the rising sun. However, various surveys of old English churches found no evidence of any such general practice.
The present-day "General Instruction of the Roman Missal does not forbid the ad orientem position for the priest when saying Mass and only requires that in new or renovated churches the facing-the-people orientation be made possible: "The altar should be built separate from the wall, in such a way that it is possible to walk around it easily and that Mass can be celebrated at it facing the people, which is desirable wherever possible." As in some ancient churches the ad orientem position was physically impossible, so today there are churches and chapels in which it is physically impossible for the priest to face the people throughout the Mass. A letter of 25 September 2000 from the "Congregation for Divine Worship and the Discipline of the Sacraments treats the phrase "which is desirable wherever possible" as referring to the requirement that altars be built separate from the wall, not to the celebration of Mass facing the people, while "it reaffirms that the position toward the assembly seems more convenient inasmuch as it makes communication easier ... without excluding, however, the other possibility." On 13 January 2008, Pope "Benedict XVI publicly celebrated Mass in the "Sistine Chapel at its altar, which is attached to the west wall. He later celebrated Mass at the same altar in the Sistine Chapel annually for the Feast of the "Baptism of the Lord. His celebration of Mass in the "Pauline Chapel in the Apostolic Palace on 1 December 2009 was reported to be the first time he publicly celebrated Mass ad orientem on a freestanding altar. In reality, earlier that year the chapel had been remodelled, with "the previous altar back in its place, although still a short distance from the tabernacle, restoring the celebration of all 'facing the Lord'." On 15 April 2010 he again celebrated Mass in the same way in the same chapel and with the same group. The practice of saying Mass at the altar attached to the west wall of the Sistine Chapel on the Feast of the Baptism of the Lord was continued by "Pope Francis, when he celebrated the feast for the first time as Supreme Pontiff on 12 January 2014. Although neither before nor after the 20th-century revision of the "Roman Rite did liturgical norms impose either orientation, the distinction became so linked with traditionalist discussion that it was considered journalistically worthy of remark that Pope Francis celebrated Mass ad orientem  at an altar at which only this orientation was possible.
In a conference in London on 5 July 2016, "Cardinal "Robert Sarah, Prefect of the Congregation for Divine Worship and the Discipline of the Sacraments, encouraged priests to adopt the ad orientem position from the first Sunday in "Advent at the end of that year. However, the "Vatican soon clarified that this was a personal view of the cardinal and that no official directives would be issued to change the prevailing practice of celebrating versus populum.
With the "English Reformation, the "Church of England directed that the sacrament of the Holy Eucharist be celebrated at a communion table placed lengthwise in the chancel or in the body of the church, with the priest standing on the north side of the holy table, facing south. Turning to the east continued to be observed at certain points of the Anglican liturgy, including the praying of the "Gloria Patri, "Gloria in Excelsis and "ecumenical creeds in that direction. "Archbishop Laud, under direction from "Charles I of England, encouraged a return to the use of the altar at the east end, but in obedience to the "rubric in the "Book of Common Prayer the priest stood at the north end of the altar. In the middle of the 19th century, the "Oxford Movement gave rise to a return to the eastward-facing position, and use of the versus populum position appeared in the second half of the 20th century.
However, over "the course of the last forty years or so, a great many of those altars have either been removed and pulled out away from the wall or replaced by the kind of freestanding table-like altar", in "response to the popular sentiment that the priest ought not turn his back to the people during the service; the perception was that this represented an insult to the laity and their centrality in worship. Thus developed today’s widespread practice in which the clergy stand behind the altar facing the people."
In the West, the tradition is first witnessed by Augustine: 'When we stand at prayer, we turn to the east (ad orientem), whence the heaven rises.'
In subsequent centuries the practice was clearly understood as rooted in Scripture and tradition and survived the Reformation in the Church of England. According to Dearmer: The ancient custom of turning to the East, or rather to the altar, for the Gloria Patri and the Gloria in Excelsis survived through the slovenly times, and is now common amongst us. (The choir also turned to the altar for the intonation of the Te Deum, and again for its last verse.) We get a glimpse of the custom after the last revision [i.e. 1662] from a letter which Archdeacon Heweston wrote in 1686 to the great Bishop Wilson (then at his ordination as deacon), telling him to ‘turn towards the East whenever the Gloria Patri and the Creeds are rehearsing’: of this and other customs he says, ‘which thousands of good people of our Church practice at this day.’ The practice here mentioned of turning to the East for the Creeds was introduced by the Caroline divines, and has established itself firmly amongst us, though it is not embodied in a rubric at the last revision as were some of the other ceremonial additions of the Laudian school. It thus rests upon a common English custom three centuries old, and it is in every way an excellent practice. But it may well be doubted whether there is any reason for turning to the East to sing that ’Confession of our Christian Faith’ which is ‘commonly called the Creed of Saint Athanasius’… the proper use is to turn to the altar only for the Gloria Patri at its conclusion. [p. 198-199] It should be made clear that showing reverence to the altar or holy table, (historically Anglicans have used these terms interchangeably with varying emphasis over the centuries), when passing it, or in coming or going from the church etc. are indications of reverence for what occurs upon it, and not to be confused with turning to the East for the Creed, or when expressly addressing the Blessed Trinity in praise. This is admittedly slightly confusing, especially in churches which do not have an actual Eastward orientation. In such cases the direction of the church is presumed to be symbolically Eastward, and facing the direction of the principal altar is taken as East-facing, but Anglicans do not, as is sometimes supposed, face the altar for the Creed etc., rather it is the altar is aligned with our actual or symbolic orientation. The Hierurgia Anglicana records that the ancient practice of Eastward recitations were still retained at Manchester Cathedral in 1870, and Procter and Frere record that the custom at Salisbury, for recitation of the Nicene Creed only, “was for the choir to face the altar at the opening words, till they took up the signing, to turn to the altar again for the bowing at the Incarnatus, and again at the last clause to face the altar until the Offertory.” [p. 391] J. Wickham Legg observed : It will be noticed how persistent has been the custom in the Church of England of turning to the East at the Apostles’ Creed. Toward the end of the nineteenth century certain persons, hangers onto the High Church school, though unworthy of that honored name, discovered that the custom was only English, and they discontinued it in their persons.” However Legg points out that it was recorded in seventeenth century France and it would seem to have been rather more widely observed than the Anglo-papalists he decries could have known. This would seem to be another instance of the liturgical conservatism of the British Church preserving a distinctive and once more universal expression of popular devotion otherwise abandoned. Another instance of orientation was the now much rarer custom of turning to the East for the Doxology at the conclusion of the recitation of each Psalm, particularly by those in choir. This was the custom at Probus in Cornwall in the early years of the nineteenth century, as it was in rural North Devon long before the influence of Puseyism: “all the singing time they used to face West, staring at the gallery, with its faded green curtains; and then; when the Gloria came, they all turned ‘right about’ and faced Eastward.” [Legg, p. 180] ... Some evangelical Anglicans argue strongly against the Eastward position, yet as we have noted its use is documented in the earliest records of the Church. They especially oppose it for the celebrant during the Holy Communion because it seems to them to imply an unacceptable theology of priestly sacrifice. In doing so they neglect to notice the arbitrariness of the North position; the South side, for example, would offer an equally unimpeded view of the celebrant’s actions. The early Reformers, who were the advocates of the North position, had in mind the instructions given in Leviticus, that the priest shall sacrifice animal offerings ‘on the side of the altar northward’ [i: 11] and as such its use implies the exact opposite of what contemporary Evangelicals presume is intended.
Many Episcopalians remember a time when the altars in most Episcopal churches were attached to the wall beyond the altar rail. The Celebrant at the Eucharist would turn to the altar and have his back – his back, never hers in those days – to the congregation during the Eucharistic Prayer and the consecration of the bread and wine. Over the course of the last forty years or so, a great many of those altars have either been removed and pulled out away from the wall or replaced by the kind of freestanding table-like altar we now use at St. Paul’s, Ivy. This was a response to the popular sentiment that the priest ought not turn his back to the people during the service; the perception was that this represented an insult to the laity and their centrality in worship. Thus developed today’s widespread practice in which the clergy stand behind the altar facing the people.