Adam Clarke on Psalms 89:51

They have reproached the footsteps of thine anointed - They search into the whole history of thy people; they trace it up to the earliest times; and they find we have been disobedient and rebellious; and on this account we suffer much, alas, deserved reproach. The Chaldee gives this clause a singular turn: "Thy enemies have reproached the slowness of the footsteps of the feet of thy Messiah, O Lord. We have trusted in him as our great Deliverer, and have been daily in expectation of his coming: but there is no deliverer, and our enemies mock our confidence." This expectation seems now wholly abandoned by the Jews: they have rejected the true Messiah, and the ground of their expectation of another is now cut off. When will they turn unto the Lord? When shall the veil be taken away from their hearts? "Bend by thy grace, O bend or break

The iron sinew in their neck!"