1 Chronicles 5:1–26 (ESV)

1 The sons of Reuben the firstborn of Israel (for he was the firstborn, but because he defiled his father’s couch, his birthright was given to the sons of Joseph the son of Israel, so that he could not be enrolled as the oldest son;

The Chronicler has gone to great lengths to establish Judah’s primacy among all of the tribes of Israel. The providential election of Judah as the vehicle of covenant favour and transmission has now become apparent from that tribe’s first place in the order of the genealogies, the proportionately greater amount of space devoted to it, and from the unexpected placement of Simeon right after Judah in the genealogy and before Reuben who had forfeited the privilege of rights as a firstborn.1 The Davidic covenant lies at the centre of what establishes Judah as the core tribe of the Israelites both historically and theologically (1 Chronicles 2:3 – 4:23).

The focus now shifts eastward to the Transjordan tribes, Reuben, Gad, and the half-tribe of Manasseh. These three tribes are grouped together because together they received their inheritance, which Moses gave them, beyond the Jordan eastward in the area traditionally known as Gilead (Joshua 13:8).2

The purpose of this passage is twofold: first, it explains the position of the prominence of Judah, the fourth-born son of Jacob (changed to Israel) above Reuben who was actually the firstborn son. And second, this section fits in with the Chronicler’s overall purpose behind compiling the Chronicles which is including all the tribes into the ideal all Israel identity he wants to instil in the postexilic community.