Deuteronomy 3:18-20

18“At that time I gave this command to the tribes that would live east of the Jordan: ‘Although the Lord your God has given you this land as your property, all your fighting men must cross the Jordan ahead of your Israelite relatives, armed and ready to assist them.

19Your wives, children, and numerous livestock, however, may stay behind in the towns I have given you.

20When the Lord has given security to the rest of the Israelites, as he has to you, and when they occupy the land the Lord your God is giving them across the Jordan River, then you may all return here to the land I have given you.’