Remember the word which Moses the servant of Yahweh commanded you, saying, Yahweh your God gives you rest, and will give you this land.
Not all the warriors from the two and one-half tribes went with (not "before," Joshua 1:14) their brethren across the Jordan. Only 40,000 of the 110,000 did (cf. Joshua 4:13 and Numbers 26:7; Numbers 26:18; Numbers 26:34). The remainder evidently stayed in Transjordan. We should understand "all" (Joshua 1:14) in this limited sense.