"To strike great kings. It is written (Amos 2:9): 'Yet it was I who destroyed the Amorite before them, whose height was like the height of cedars and who was as strong as oaks; I destroyed his fruit above and his roots below.' Our sages said that Sihon was as hard as a tower and wall, and harder than any other creature, taller than any tower, and his feet touched the ground and no creature in the world could stand before him.
What did the Holy One, blessed be He, do? He caused one of His ministering angels to strike him, as it is said (Num. 21:35): 'And I destroyed his fruit from above and his roots from below.' And he dislodged him from his place and delivered him to Israel. Our sages said that Sihon and Og were harder than Pharaoh and his soldiers.
Just as they said a song of praise over the defeat of Pharaoh, so were they worthy of saying a song of praise over the defeat of Sihon and Og, but then David came and said a song over them, as it is said (Psalm 136:18-20): 'To strike down great kings, for His mercy endures forever; and Og, king of Bashan, for His mercy endures forever.' Rabbi Shimon ben Lakish said in the name of Bar Kapara: His name was Pelit, as it is said (Gen. 14:13): 'And he who had escaped [Pelit] came and told Abram the Hebrew.'
And why was he called Og? Because he came and found Abraham engaged in making matzah for Passover. When Moses and the Israelites came to the border of Edrei, Moses said to them, "I will camp here tonight, and in the morning we will enter and conquer it." They camped there, but the spring was not visible.
Moses looked up and saw Og sitting on the wall, his feet touching the ground. Moses said, "I don't know what I'm seeing. A different wall has been built here tonight." The Holy One, blessed be He, said to him, "That is Og whom you see."
Rabbi Yochanan said that his legs were 18 cubits long. Og had uprooted a mountain and was throwing it at the Israelites. Moses took a beam, inscribed the explicit Name of God upon it, and threw it at Og. Israel said, "Cursed be the hands that throw." The Amorites said, "Cursed be the hands that support."