John Gill Commentary Psalms 51:16

"For thou delightest not in sacrifice; else would I give it: Thou hast no pleasure in burnt-offering." — Psalms 51:16 (ASV)

For you desire not sacrifice
Legal sacrifice; for there was no sacrifice appointed under the law for murder and adultery;

else would I give [it] ;
he would gladly have offered it up;

you delight not in burnt offering ;
at least such kind of sacrifices, though they were of divine appointment, and at that time in full force and use; yet they were not the only and principal sacrifices God desired and delighted in; nor were they at all acceptable to him without faith in Christ, and an humble sense of sin; and when offered in the best manner, yet spiritual obedience, acts of mercy, and sacrifices of praise and thanksgiving, were more pleasing to him, (1 Samuel 15:15 1 Samuel 15:22) (Hosea 6:6) (Psalms 69:30Psalms 69:31) ; therefore the psalmist proposed to offer praise in (Psalms 51:15) , and adds what follows.