Numbers 32:23-27

But if ye will not do so, behold, ye have sinned against the LORD: and be sure your sin will find you out. Build you cities for your little ones, and folds for your sheep; and do that which hath proceeded out of your mouth. And the children of Gad and the children of Reuben spake unto Moses, saying, Thy servants will do as my lord commandeth. Our little ones, our wives, our flocks, and all our cattle, shall be there in the cities of Gilead: but thy servants will pass over, every man armed for war, before the LORD to battle, as my lord saith.