Joshua 13:8, 10, 24-28

With the other half-tribe [of Manasseh], the Reubenites and the Gadites received their inheritance which Moses gave them beyond the Jordan eastward, just as Moses the servant of the LORD gave to them

and all the cities of Sihon king of the Amorites, who reigned in Heshbon, as far as the border of the Ammonites

Moses also gave an inheritance to the tribe of Gad, to the sons of Gad, according to their families. Their territory was Jazer, and all the cities of Gilead, and half the land of the sons of Ammon, as far as Aroer east of Rabbah; and from Heshbon as far as Ramath-mizpeh and Betonim, and from Mahanaim as far as the border of Debir; and in the valley, Beth-haram and Beth-nimrah and Succoth and Zaphon, the rest of the kingdom of Sihon king of Heshbon, with the Jordan as a border, as far as the lower end of the Sea of Chinnereth (Galilee) east of the Jordan. This is the inheritance of the sons of Gad according to their families, with their cities and their villages.