It will be noticed that in this chapter Cassian [c. 330 – 426] alludes to five offices: (1) A morning office; (2) the third hour; (3) the sixth hour; (4) the ninth; and (5) Vespers; and gives the grounds for their observance. Similar grounds are given by Cyprian [Bishop/martyr c. 200 – 258], De Orat.Dominica sub fine:
For upon the disciples, at the third hour, the Holy Spirit descended, who fulfilled the grace of the Lord’s promise. Moreover, at the sixth hour, Peter, going up to the housetop, was instructed as well by the sign as by the word of God, admonishing him to receive all to the grace of salvation, whereas he was previously doubtful of the receiving of the Gentiles to baptism. As from the sixth to the ninth the Lord, being crucified, washed away our sins by His blood; and that He might redeem and quicken us, He then accomplished His victory by His passion. But for us, beloved brethren, besides the hours of prayer observed of old… the times…have now increased in number. For we must also pray in the morning, that the Lord’s resurrection may be celebrated by morning prayer. . .. Also at the sun-setting and decline of day we must pray again. For since Christ is the true Sun and the Day, as the worldly sun and day depart, when we pray and ask that light may return to us again, we pray for the advent of Christ, which shall give us the grace of everlasting light. Cf. also S. Basil [c. 330 – 379], The Greater Monastic Rules, Q xxxvii., where the same subject is discussed, and Apost. Const. Book VIII. c.xxxiv. In later times the Seven Canonical Hours were all connected with the events of our Lord’s Passion, and supposed to commemorate His sufferings, as the following stanzas show:
At Mattins bound, at Prime reviled,
Condemned to death at Tierce,
Nailed to the Cross at Sext, at Nones
His blessed side they pierce.
They take him down at Vesper-tide,
In grave at Compline lay;
Who thenceforth bids His Church observe
Her sevenfold hour always.
Chapter III, Book III, ’Of The Canonical System Of The Daily Prayers and Psalms,’ The Institutes of John Cassian in A Select Library of Nicene and Post-Nicene Fathers of the Christian Church, Second Series, ed. Schaff and Wace, Eerdmans, Grand Rapids, reprinted 1986.