Sforno on Numbers 32:28/ספורנו על במדבר ל״ב:כ״ח

1ויצו להם, Moses now commanded not to give to these two tribes the lands of Sichon and Og until they would return from conquest of the lands on the west bank of the river Jordan. This is the meaning of verse 22. The two tribes did not accept this arrangement and said נחנו נעבור חלוצים (verse 32) on condition that אתנו אחזת נחלתנו, that simultaneously we will be in possession of our ancestral inheritance. As soon as we shall cross the river Jordan these lands will be legally ours!