The Apostolic Constitutions Bk. 1 § 2 chap. 5:
Or if thou stayest at home, read the books of the Law, of the Kings, with the Prophets; sing the hymns of David; and peruse diligently the Gospel, which is the completion of the other.
Bk. 1 § 2 chap. 6:
If thou desirest something to sing, thou hast the Psalms...
Bk. 2 § 7 chap. 57:
But when there have been two lessons severally read, let some other person sing the hymns of David, and let the people join at the conclusions of the verses.
Bk. 2 § 7 chap. 59:
Be not careless of yourselves, neither deprive your Saviour of His own members, neither divide His body nor disperse His members, neither prefer the occasions of this life to the word of God; but assemble yourselves together every day, morning and evening, singing psalms and praying in the Lord’s house: in the morning saying the sixty-second Psalm, and in the evening the hundred and fortieth, but principally on the Sabbath-day.
Also ascribed to the Apostolic Constitutions by Gilbert McMaster in his An Apology for the Book of Psalms in Five Letters, p. 58:
The women, the children, and the humblest mechanics, could repeat all the Psalms of David; they chanted them at home and abroad: they made them the exercises of their piety and the refreshment of their minds. Thus they had answers ready to oppose temptation, and were always prepared to pray to God, and to praise him, in any circumstance, in a form of his own inditing.