Psalms 89:51 - Joseph Benson’s Commentary on the Old and New Testaments

Wherewith thine enemies have reproached the footsteps of thine anointed Or, of the Messiah. By whom he seems to understand, either, 1st, The kings of Judah, the singular number being put for the plural; and by their footsteps may be meant either their ways or actions, and the sad consequences thereof, or the memorials of their ancient splendour. Or, 2d, The Messiah himself, whose coming the Jews continually expected, for a long time together before he came, and supported themselves with the expectation of him under all their calamities. All which being well known to many of the heathen, they reproached the Jews with the vanity of this belief and expectation. And by the footsteps of the Messiah he may understand his coming.