Acts 10:9

Stated hours for prayer were appointed both in the old and new law. Of this St. Cyprian writes: "In celebrating their prayers, we find that the three children of Daniel observed the third, sixth, and ninth hour. Thus afterwards, at the third hour, the Holy Ghost descended upon the apostles, fulfilling the grace of our Lord's promise: at the sixth hour, Peter going up to the higher room of the house, was both by voice and sign from God instructed, that all nations should be admitted to the grace of salvation, of which he before doubted; and our Lord being crucified at the sixth hour, at the ninth hour washed away our sins by his blood. But to us, besides the seasons observed of old, the set times of praying are increased; for we must pray in the morning early, that the resurrection of our Lord may be celebrated by morning prayer; in the morning early will I stand before Thee, early in the morning wilt thou hear my voice. (Psalm v.) Towards the evening also, when the sun departeth, we must of necessity pray again." (De Orat. Dom. No. 15) St. Jerome, writing to Eustochia, a virgin, and a religious, (ep. 22.) says, "though the apostles bid us to pray always, and, to holy persons, their very sleep is prayer; yet we must have distinct hours for prayer, that if perhaps we be otherwise occupied, the very time may admonish us of our duty. The third, sixth, ninth hour, morning early, and evening, no man can be ignorant of.