Numbers 32:20-27

20Then Moses said to them: “If you do this thing, if you arm yourselves before the Lord for the war,

21and all your armed men cross over the Jordan before the Lord until He has driven out His enemies from before Him,

22and the land is subdued before the Lord, then afterward you may return and be blameless before the Lord and before Israel; and this land shall be your possession before the Lord.

23But if you do not do so, then take note, you have sinned against the Lord; and be sure your sin will find you out.

24Build cities for your little ones and folds for your sheep, and do what has proceeded out of your mouth.”

25And the children of Gad and the children of Reuben spoke to Moses, saying: “Your servants will do as my lord commands.

26Our little ones, our wives, our flocks, and all our livestock will be there in the cities of Gilead;

27but your servants will cross over, every man armed for war, before the Lord to battle, just as my lord says.”