Numbers 32:29 (KJV)

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.

So concerning them Moses commanded Eleazar the priest, and Joshua the son of Nun, and the chief fathers of the tribes of the children of Israel:

But if they will not pass over with you armed, they shall have possessions among you in the land of Canaan.

And the children of Gad and the children of Reuben answered, saying, As the LORD hath said unto thy servants, so will we do.

We will pass over armed before the LORD into the land of Canaan, that the possession of our inheritance on this side Jordan may be ours.

And Moses gave unto them, even to the children of Gad, and to the children of Reuben, and unto half the tribe of Manasseh the son of Joseph, the kingdom of Sihon king of the Amorites, and the kingdom of Og king of Bashan, the land, with the cities thereof in the coasts, even the cities of the country round about.

And the children of Gad built Dibon, and Ataroth, and Aroer,