1 Chronicles 5:9
And eastward he inhabited unto the entering in of the wilderness from the river Euphrates: because their cattle were multiplied in the land of Gilead. And eastward he inhabited unto the entering in of the wilderness from the river Euphrates: because their cattle were multiplied in the land of Gilead.
The verse stands in Chronicles, a book that supplies information omitted from Samuel and Kings. That book gives extensive place to genealogies. After the exile those genealogies served a practical purpose in documenting hereditary descent. That documentation governed the assigning of land and the maintaining of temple service.
The verse records that the descendants of Reuben dwelt eastward as far as the entrance of the wilderness from the river Euphrates. The reason was that their cattle had multiplied in the land of Gilead and needed more room. The preservation of such details of territory and livestock shows that genealogies keep particular facts about people and their lives. In the same way a faithful record of every soul is kept in heaven.