משנה אויף במדבר 32:6

Rabbi Meir says: every stipulation which is not like that of the children of Gad and the children of Reuben is not a [valid] stipulation, as it say, “And Moses said to them, ‘If the children of Gad and the children of Reuben will pass [with you over the Jordan, then you shall give them the land of Gilead for a possession].” and it is also written, “But if they will not pass over with you armed, [then they shall have possessions among you in the land of Canaan]” (Numbers 32:29-30). Rabbi Hanina ben Gamaliel says: the matter had to be stated, for had it not been stated it would have implied that even in Canaan they should not inherit.