16 Observe how not only concerning a cool place, but neither of that very fire to be desired he has been silent: “I will enter into Your House in holocausts”. What is a holocaust? A whole sacrifice burned up, but with fire divine. For a sacrifice is called a holocaust, when the whole is burned. One thing are the parts of sacrifices, another thing a holocaust: when the whole is burned and the whole consumed by fire divine, it is called a holocaust: when a part, a sacrifice. Every holocaust indeed is a sacrifice: but not every sacrifice a holocaust. Holocausts therefore he is promising, the Body of Christ is speaking, the Unity of Christ is speaking, “I will enter into Your House in holocausts.” All that is mine let Your fire consume, let nothing of mine remain to me, let all be Yours. But this shall be in the Resurrection of just men, “when both this corruptible shall be clad in incorruption, and this mortal shall be clad in immortality: then shall come to pass that which has been written, 'Death is swallowed up in victory.'” Victory is, as it were, fire divine: when it swallows up our death also, it is a holocaust. There remains not anything mortal in the flesh, there remains not anything culpable in the spirit: the whole of mortal life shall be consumed, in order that in life everlasting it may be consummated, that from death we may be preserved in life. These therefore will be the holocausts. And what shall there be “in the holocausts”?
17. “I will render to You my vows, which my lips have distinguished”. What is the distinction in vows? This is the distinction, that yourself thou censure, Him thou praise: perceive yourself to be a creature, Him the Creator: yourself darkness, Him the Enlightener, to whom you should say, “You shall light my lamp, O Lord my God, You shall enlighten my darkness.” For whenever you shall have said, O soul, that from yourself you have light, you will not distinguish. If you will not distinguish, you will not render distinct vows. Render distinct vows, confess yourself changeable, Him unchangeable: confess yourself without Him to be nothing, but Himself without you to be perfect; yourself to need Him, but Him not to need you. Cry to Him, “I have said to the Lord, My God are You, for my good things You need not.” Now though God takes you to Him for a holocaust, He grows not, He is not increased, He is not richer, He becomes not better furnished: whatsoever He makes of you for your sake, is the better for you, not for Him that makes. If you distinguish these things, you render the vows to your God which your lips have distinguished.
18. “And my mouth has spoken in my tribulation.” How sweet ofttimes is tribulation, how necessary! In that case what has the mouth of the same spoken in his tribulation? “Holocausts marrowed I will offer to You”. What is “marrowed”? Within may I keep Your love, it shall not be on the surface, in my marrow it shall be that I love You. For there is nothing more inward than our marrow: the bones are more inward than the flesh, the marrow is more inward than those same bones. Whosoever therefore on the surface loves God, desires rather to please men, but having some other affection within, he offers not holocausts of marrow: but into whosesoever marrow He looks, him He receives whole. “With incense and rams.” The rams are the rulers of the Church: the whole Body of Christ is speaking: this is the thing which he offers to God. Incense is what? Prayer. “With incense and rams.” For especially the rams do pray for the flocks. “I will offer to You oxen with he-goats.” Oxen we find treading out grain, and the same are offered to God. The Apostle has said, that of the preachers of the Gospel must be understood that which has been written, “Of the ox treading out grain the mouth you shall not muzzle. Does God care for oxen?” Therefore great are those rams, great the oxen. What of the rest, that perchance are conscious of certain sins, that perchance in the very road have slipped, and, having been wounded, by penitence are being healed? Shall they too continue, and to the holocausts shall they not belong? Let them not fear, he has added he-goats also. “I will offer to You oxen with he-goats.” By the very yoking are saved the he-goats; of themselves they have no strength, being yoked to bulls they are accepted. For they have made friends of the mammon of iniquity, that the same may receive them into everlasting tabernacles. Therefore those he-goats shall not be on the left, because they have made to themselves friends of the mammon of iniquity. But what he-goats shall be on the left? They to whom shall be said, “I hungred, and you gave me not to eat:” not they that have redeemed their sins by almsdeeds.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)