Deuteronomy 3:2
And the LORD said unto me, Fear him not: for I will deliver him, and all his people, and his land, into thy hand; and thou shalt do unto him as thou didst unto Sihon king of the Amorites, which dwelt at Heshbon. And the LORD said unto me, Fear him not: for I will deliver him, and all his people, and his land, into thy hand; and thou shalt do unto him as thou didst unto Sihon king of the Amorites, which dwelt at Heshbon.
The promise belongs to Israel's advance into Bashan, a powerful and populous kingdom of fortified cities built of stone and ruled by Og, a king of gigantic size. The Lord spoke to Moses commanding him not to fear Og king of Bashan, for He would deliver the king himself, all his people, and his land into Israel's hand. Israel was to deal with Og exactly as it had dealt with Sihon king of the Amorites who dwelt at Heshbon.
The assurance was given in the face of daunting odds, for Og was a man of great size and stature, commanding a large army from a seemingly impregnable stronghold and a strong position at Edrei. That word gave Moses courage and confidence to lead Israel forward against Og and his forces. It also steadied and strengthened all Israel, enabling them to face Og's army and fortress in confidence rather than dread.
God fulfilled what He had promised by Himself conquering and defeating Og and his army and forces, bringing Israel victory and giving Israel possession of the country and land. Together with the defeat of Sihon and the crossing of the Jordan, the defeat of Og stood as proof to Israel and to the surrounding nations that God was with His people and would not forsake them.