Charles H. Spurgeon on Psalms 136:20

Og the king of Bashan. There is continued victory. The second hindrance disappears after the first. "Og, king of Bashan", last of the giants (De 3:11), fared no better for all his strength than Sihon. It was not some peculiar weakness of Sihon that overthrew him. All enemies of God, however different in resource they may appear when they measure themselves among themselves, are alike to those who march in the strength of God. The power by which the Christian conquers one foe will enable him to conquer all. And yet because Og did look more formidable than Sihon, God gave his people special encouragement in meeting him: Nu 21:34. God remembers that even the most faithful and ardent of his people cannot get entirely above the deceitfulness of outward appearances. —Pulpit Commentary.