Albert Barnes Commentary Psalms 51:19

"Then will thou delight in the sacrifices of righteousness, In burnt-offering and in whole burnt-offering: Then will they offer bullocks upon thine altar." — Psalms 51:19 (ASV)

Then shalt thou be pleased with the sacrifices of righteousness - “Then,” that is, when God shall have thus shown favor to Zion; when He shall have poured out His blessing on Jerusalem; when religion shall prosper and prevail; and when there shall be an increase of the pure worship of God.

In such offerings as would then be made—sacrifices presented not in mere form, but with sincerity, humility, and penitence; the outward offering of blood presented with a corresponding sincerity of feeling, with true contrition, and with a proper acknowledgment of the guilt designed to be represented by the shedding of blood in sacrifice—God would be pleased and would approve the worship thus rendered to Him.

Sacrifice would then be acceptable, for it would not be presented as a mere form. Instead, it would be offered in such a way that it might be called a sacrifice of righteousness—a sacrifice offered with a right spirit, in a manner which God would deem right.

With burnt-offering - See the notes at Isaiah 1:11.

And whole burnt-offering - The word here means that which is wholly consumed, no part of which was reserved to be eaten by the priests, as was the case in many of the sacrifices. See Deuteronomy 33:10. Compare Leviticus 6:9 and Leviticus 1:3-17.

Then shall they offer bullocks upon thine altar - That is, bullocks shall then be offered.

The meaning is that all the offerings prescribed in the law would then be brought, and those sacrifices would be made with a right spirit—a spirit of true devotion, the offering of the heart accompanying the outward form. In other words, the spirit of humble worship and of pure religion would be manifested.