Charles Ellicott Commentary Deuteronomy 3:21-22

"And I commanded Joshua at that time, saying, Thine eyes have seen all that Jehovah your God hath done unto these two kings: so shall Jehovah do unto all the kingdoms whither thou goest over. Ye shall not fear them; for Jehovah your God, he it is that fighteth for you." — Deuteronomy 3:21-22 (ASV)

I commanded Joshua at that time... . Thine eyes have seen. —“Your eyes are the witnesses of all.” The conquest of Sihon and Og, as well as that of Amalek, was to be impressed upon Joshua as a precedent for his encouragement and also for his instruction.

It is remarkable that no details are given to us of the battles against Sihon and Og, or of the capture of the cities, except in Joshua 12:6, Them did Moses the servant of the Lord smite. We see the reflection of Moses’ campaign, which is unwritten, in the recorded campaigns of Joshua. The peculiar form of the sentence, “Your eyes are they that see,” may also serve to remind us of the fact that, though the Law was given by Moses, no eye saw its full breadth and grasp until it came into the hand of Jesus, the antitype of Joshua.