On the Recitation of the 12 Psalms

In reading "The Sayings of the Desert Fathers" by Benedicta Ward, I came across a reference to the twelve psalms: "When evening came, they recited the twelve psalms and went to sleep." Does anyone know which twelve psalms they recited? The quote was in the Rho section, under "An Abba of Rome (This is almost certainly Arsenius)". Was this an early codification of psalms to be said at eveningtime?

RE: THE TWELVE PSALMS

Summary: Psalmody

EXCERPTS FROM THE TWELVE BOOKS OF JOHN CASSIAN ON THE INSTITUTES OF THE COENOBIA, AND THE REMEDIES FOR THE EIGHT PRINCIPAL FAULTS.

CHAPTER IV.

How throughout the whole of Egypt and the Thebaid the number of Psalms is fixed at twelve.

So, as we said, throughout the whole of Egypt and the Thebaid the number of Psalms is fixed at twelve both at Vespers and in the office of Nocturns, in such a way that at the close two lessons follow, one from the Old and the other from the New Testament. And this arrangement, fixed ever so long ago, has continued unbroken to the present day throughout so many ages, in all the monasteries of those districts, because it is said that it was no appointment of man's invention, but was brought down from heaven to the fathers by the ministry of an angel.

CHAPTER V.

How the fact that the number of the Psalms was to be twelve was received from the teaching of an angel.

For in the early days of the faith when only a few, and those the best of men, were known by the name of monks, who, as they received that mode of life from the Evangelist Mark of blessed memory, the first to preside over the Church of Alexandria as Bishop, not only preserved those grand characteristics for which we read, in the Acts of the Apostles, that the Church and multitude of believers in primitive times was famous ("The multitude of believers had one heart and one soul. Nor did any of them say that any of the things which he possessed was his own: but they had all things common; for as many as were owners of lands or houses sold them, and brought the price of the things which they sold, and laid it at the feet of the Apostles, and distribution was made to every man as he had need"), but they added to these characteristics others still more sublime. For withdrawing into more secluded spots outside the cities they led a life marked by such rigorous abstinence that even to those of another creed the exalted character of their life was a standing marvel. For they gave themselves up to the reading of Holy Scripture and to prayers and to manual labour night and day with such fervour that they had no desire or thoughts of food--unless on the second or third day bodily hunger reminded them, and they took their meat and drink not so much because they wished for it as because it was necessary for life; and even then they took it not before sunset, in order that they might connect the hours of daylight with the practice of spiritual meditations, and the care of the body with the night, and might perform other things much more exalted than these. And about these matters, one who has never heard anything from one who is at home in such things, may learn from ecclesiastical history. At that time, therefore, when the perfection of the primitive Church remained unbroken, and was still preserved fresh in the memory by their followers and successors, and when the fervent faith of the few had not yet grown lukewarm by being dispersed among the many, the venerable fathers with watchful care made provision for those to come after them, and met together to discuss what plan should be adopted for the daily worship throughout the whole body of the brethren; that they might hand on to those who should succeed them a legacy of piety and peace that was free from all dispute and dissension, for they were afraid that in regard of the daily services some difference or dispute might arise among those who joined together in the same worship, and at some time or other it might send forth a poisonous root of error or jealousy or schism among those who came after. And when each man in proportion to his own fervour--and unmindful of the weakness of others--thought that that should be appointed which he judged was quite easy by considering his own faith and strength, taking too little account of what would be possible for the great mass of the brethren in general (wherein a very large proportion of weak ones is sure to be found); and when in different degrees they strove, each according to his own powers, to fix an enormous number of Psalms, and some were for fifty, others sixty, and some, not content with this number, thought that they actually ought to go beyond it,--there was such a holy difference of opinion in their pious discussion on the rule of their religion that the time for their Vesper office came before the sacred question was decided; and, as they were going to celebrate their daily rites and prayers, one rose up in the midst to chant the Psalms to the Lord. And while they were all sitting (as is still the custom in Egypt, with their minds intently fixed on the words of the chanter, when he had sung eleven Psalms, separated by prayers introduced between them, verse after verse being evenly enunciated he finished the twelfth with a response of Alleluia, and then, by his sudden disappearance from the eyes of all, put an end at once to their discussion and their service.

CHAPTER VI.

Of the Custom of having Twelve Prayers.

Whereupon the venerable assembly of the Fathers understood that by Divine Providence a general rule had been fixed for the congregations of the brethren through the angel's direction, and so decreed that this number should be preserved both in their evening and in their nocturnal services; and when they added to these two lessons, one from the Old and one from the New Testament, they added them simply as extras and of their own appointment, only for those who liked, and who were eager to gain by constant study a mind well stored with Holy Scripture. But on Saturday and Sunday they read them both from the New Testament; that is, one from the Epistles or the Acts of the Apostles, and one from the Gospel. And this also those do whose concern is the reading and the recollection of the Scriptures, from Easter to Whitsuntide [Pentecost].