How no change was made by the Elders in the ancient system of Psalms when the Mattin office was instituted.
But this too we ought to know, viz., that no change was made in the ancient arrangement of Psalms by our Elders who decided that this Mattin service should be added; 741 but that office 742 was always celebrated in their nocturnal assemblies according to the same order as it had been before. For the hymns which in this country they used at the Mattin service at the close of the nocturnal vigils, which they are accustomed to finish after the cock-crowing and before dawn, these they still sing in like manner; viz., Ps. 148, beginning “O praise the Lord from heaven,” and the rest which follow; but the 50th Psalm and the 62nd, and the 89th have, we know, been assigned to this new service. Lastly, throughout Italy at this day, when the Mattin hymns are ended, the 50th Psalm is sung in all the churches, which I have no doubt can only have been derived from this source.
I.e., Prime. Some confusion is likely to be caused by the fact that Cassian speaks of both “Lauds” and “Prime” by the same title of Mattins. Immediately below, where he speaks of the “Mattin service at the close of the nocturnal vigils” he is referring to Lauds, which always followed immediately (or after a very short interval) after Nocturns, or Mattins. At this service Psa. 148-150. have always been sung, indeed, they form the characteristic feature which gives the service its name of “Lauds” (οἱ ἆινοι). Of the other three Ps. 51:0, Ps. 63:0, Ps. 90:0, which Cassian says had been transferred from Lauds to the newly instituted service of Prime, Psa. 63 has been already spoken of as a morning hymn of the early Church (see the notes on c. iii.), and we learn from S. Basil that in his day Psa. 51 (ὁ τἠς ἐξομολογήσεως ψαλμός) was regularly sung after Mattins when the day began to break (Ep. ccvii. ad clericos Neo-Cæs.), and it is still a Lauds Psalm in both East and West. Psa. 90 is now one of the fixed Psalms at Prime in the East, but in the West it is, according to the Roman rule, sung at Lauds on Thursdays only. Thus it would appear that the transfer of these three Psalms from Lauds to Prime, of which Cassian speaks, never obtained widely, but that the older arrangement, whereby, at any rate, Ps. 51:0, Ps. 63:0 were assigned to Lauds, has generally been adhered to both in the East and West. Cf. the Rule of S. Benedict, according to which Psa. 51 is sung daily at Lauds, and Psa. 63 as well on Sundays (c. xii., xiii.).216:742