Numbers 32:20-24

20Then Moses said to them, “If you will do this—if you will arm yourselves before the Lord for battle 21and if all of you who are armed cross over the Jordan before the Lord until he has driven his enemies out before him— 22then when the land is subdued before the Lord, you may return and be free from your obligation to the Lord and to Israel. And this land will be your possession before the Lord. 23“But if you fail to do this, you will be sinning against the Lord; and you may be sure that your sin will find you out. 24Build cities for your women and children, and pens for your flocks, but do what you have promised.”