Note that vs. 18-19 contradict the verses immediately before them. Vs. 18-19 are believed to be added to justify temple sacrifices as that is the funding mechanism for the Priests and Monarchy.
Psalms 51:16-19 RSV
16 For thou hast no delight in sacrifice; were I to give a burnt offering, thou wouldst not be pleased.
17 The sacrifice acceptable to God is a broken spirit; a broken and contrite heart, O God, thou wilt not despise.
Interpolation Follows:
18 Do good to Zion in thy good pleasure; rebuild the walls of Jerusalem, 19 then wilt thou delight in right sacrifices, in burnt offerings and whole burnt offerings; then bulls will be offered on thy altar.
