Charles Ellicott Commentary Psalms 51:18

"Do good in thy good pleasure unto Zion: Build thou the walls of Jerusalem." — Psalms 51:18 (ASV)

Do good. — The last two verses have caused much controversy. They do not fit well with the theory of Davidic authorship, with Theodoret saying long ago that they were better suited to the exiles in Babylon.

These verses also seem at first sight to contradict what has just been asserted about sacrifice. On both grounds, they have been regarded as a liturgical addition, such as the compiler doubtless made, without any sense of infringing on the rights of authorship.

On the other hand, it is not only these two verses that harmonize with the feelings of the restored exiles, but the whole psalm. Furthermore, the contradiction regarding the worth of sacrifices is only apparent.

While vindicating spiritual religion, the psalmist no more abrogates ceremonies than the prophets do. As soon as their performance becomes possible, they will be resumed.