8 Before all things, the Teacher of peace and the Master of unity would not have prayer to be made singly and individually, as for one who prays to pray for himself alone. For we say not “My Father, which art in heaven,” nor “Give me this day my daily bread;”nor does each one ask that only his own debt should be forgiven him; nor does he request for himself alone that he may not be led into temptation, and delivered from evil. Our prayer is public and common; and when we pray, we pray not for one, but for the whole people, because we the whole people are one.
The God of peace and the Teacher of concord, who taught unity, willed that one should thus pray for all, even as He Himself bore us all in one. This law of prayer the three children observed when they were shut up in the fiery furnace, speaking together in prayer, and being of one heart in the agreement of the spirit; and this the faith of the sacred Scripture assures us, and in telling us how such as these prayed, gives an example which we ought to follow in our prayers, in order that we may be such as they were: “Then these three,” it says, “as if from one mouth sang an hymn, and blessed the Lord.” They spoke as if from one mouth, although Christ had not yet taught them how to pray.
And therefore, as they prayed, their speech was availing and effectual, because a peaceful, and sincere, and spiritual prayer deserved well of the Lord. Thus also we find that the apostles, with the disciples, prayed after the Lord's ascension: “They all,” says the Scripture, “continued with one accord in prayer, with the women, and Mary who was the mother of Jesus, and with His brethren.” They continued with one accord in prayer, declaring both by the urgency and by the agreement of their praying, that God, “who makes men to dwell of one mind in a house,” only admits into the divine and eternal home those among whom prayer is unanimous.
Source: The Treatises of Cyprian (New Advent)