Numbers 32:16-23

And they came near unto him, and said, We will build sheepfolds here for our cattle, and cities for our little ones: but we ourselves will be ready armed to go before the children of Israel, until we have brought them unto their place: and our little ones shall dwell in the fortified cities because of the inhabitants of the land. We will not return unto our houses, until the children of Israel have inherited every man his inheritance. For we will not inherit with them on the other side of the Jordan, and forward; because our inheritance is fallen to us on this side of the Jordan eastward. And Moses said unto them, If ye will do this thing, if ye will arm yourselves to go before Jehovah to the war, and every armed man of you will pass over the Jordan before Jehovah, until he hath driven out his enemies from before him, and the land is subdued before Jehovah; then afterward ye shall return, and be guiltless towards Jehovah, and towards Israel; and this land shall be unto you for a possession before Jehovah. But if ye will not do so, behold, ye have sinned against Jehovah; and be sure your sin will find you out.