Augustine of Hippo

"Voluntarily I will sacrifice to You" [Psalm 54:6]. Who can even understand this good thing of the heart, at another's speaking thereof, unless in himself he has tasted it? What is, "Voluntarily I will sacrifice to You"?... For what sacrifice here shall I take, brethren? Or what worthily shall I offer to the Lord for His mercy? Victims shall I seek from flock of sheep, ram shall I select, for any bull in the herds shall I look out, frankincense indeed from the land of the Sabæans shall I bring? What shall I do? …

Exposition on Psalm 54 ↗

Hilary of Poitiers

For next there follows: I will sacrifice unto You freely. The sacrifices of the Law, which consisted of whole burnt-offerings and oblations of goats and of bulls, did not involve an expression of free will, because the sentence of a curse was pronounced on all who broke the Law. Whoever failed to sacrifice laid himself open to the curse. And it was always necessary to go through the whole sacrificial action because the addition of a curse to the commandment forbad any trifling with the obligation of offering. …

Homilies On Psalm 53 (54).13 ↗

Thomas Aquinas

"I will sacrifice willingly to you." Here he sets forth the recompense. And first the recompense is set forth. Second, the reason for the recompense. He intends to offer as recompense two things: sacrifice and confession. With regard to the first he says, "I will sacrifice willingly to you." Against this, above he said: "if you had desired sacrifice, I would have given it." And it must be said that here he speaks of the sacrifice that is acceptable to God, which is the sacrifice of a contrite spirit and the chastisement of the body. …

Exposition on the Psalms of David ↗