Psalms 136:17

To him which smote great kings
Either the thirty one kings in the land of Canaan; or those who are after particularly mentioned; which seems best, since the kings of Canaan were petty kings, when these were greater ones;

for his mercy [endureth] for ever;
the smiting of those kings were in mercy to Israel; both to preserve them from falling into their hands, and that they might possess their countries, as is later declared.