Numbers 32:23-27

But if you fail to keep your word, then you will have sinned against the LORD, and you may be sure that your sin will find you out. Go ahead and build towns for your families and pens for your flocks, but do everything you have promised.” Then the men of Gad and Reuben replied, “We, your servants, will follow your instructions exactly. Our children, wives, flocks, and cattle will stay here in the towns of Gilead. But all who are able to bear arms will cross over to fight for the LORD, just as you have said.”