John Calvin Commentary Deuteronomy 3:18

"And I commanded you at that time, saying, Jehovah your God hath given you this land to possess it: ye shall pass over armed before your brethren the children of Israel, all the men of valor." — Deuteronomy 3:18 (ASV)

And I commanded you at that time. This address is directed only to those to whom an inheritance was given on the other side of Jordan; but Moses declares that he had introduced an agreement that the two tribes and a half should not enjoy their possession until they had accompanied their brethren in the subjugation of the land of Canaan.

He says, therefore, that he had given them a place, not where they were at once to settle themselves, but where they might deposit their wives and cattle, until the whole people were peaceably established in their land.