Numbers 35:14-15

Numbers 35:14. Three cities on this side Jordan, and three cities—in the land of Canaan— This appears not to be an equal partition, the land of Canaan being much larger than the territory beyond Jordan; for it contained about three parts in four of the tribes of Israel: but it is to be considered, that the country beyond Jordan was as long as the land of Canaan, though not so broad; besides, God commanded those in Canaan, if he enlarged their coasts to add three cities more besides these; Deuteronomy 19:8-9.

See commentary on Num 35:6