At the sixth hour likewise pray also, for, after Christ was nailed to the wood of the cross, the day was divided and there was a great darkness; wherefore let [the faithful] pray at that hour with an effectual prayer, likening themselves to the voice of him who prayed [and] caused all creation to become dark for the unbelieving Jews.
And at the ninth hour let a great prayer and a great thanksgiving be made, such as made by the souls of the righteous ones, blessing the Lord, the God who does not lie, who was mindful of his saints and sent forth his Word to enlighten them. At that hour, therefore, Christ poured forth from His pierced side water and blood, and brought the rest of the time of that day with light to evening; so, when He fell asleep, by making the beginning of another day He completed the pattern of His resurrection.
Pray again before thy body rests on thy bed.
At midnight arise, wash thy hands with water and pray. And if thy wife is with thee, pray ye both together; but if she is not yet a believer, go into another room and pray, and again return to thy bed; be not slothful in prayer. (Apostolic Tradition 36)