Nicetas of Remesiana

We know that later on the apostles also [sang psalms and hymns], since not even in prison did they cease to sing. So, too, Paul speaks to the prophets of the church: “When you come together, each of you has a hymn, has an instruction, has a revelation, has a tongue, has an interpretation. Let all things be done for edification.” And again, in another place: “I will sing with the spirit, but I will sing with the understanding also.” So, too, James sets down in his epistle: “Is any one of you sad? Let him pray. Is any one in good spirits? Let him sing a hymn.” And John in the Apocalypse reports that when the Spirit revealed himself to him, he saw and heard “a voice of the heavenly army, as it were the voice of many waters and as the voice of mighty thunders, saying, Alleluia.” From all this we may conclude that no one should doubt that this ministry, if only it is celebrated with true faith and devotion, is one with that of the angels, who, as we know, unhindered by sleep or other occupation, cease not to praise the Lord in heaven and to bless the Savior.

If he is the Spirit of adoption and makes men sons of God, how can he be considered a slave, since no slave can legitimately make another free?