דברי הימים א, פרק ה׳, פסוק ג׳

The genealogical record briefly pauses to address Reuben’s complicated standing among his brothers, only to pick up the thread again to trace his actual descendants [ביאור שטיינזלץ]. Restating his lineage serves to reset the narrative flow and restart the description of his dynasty after this brief detour [רד״ק, רש״י].

Although the practical privileges of the firstborn—specifically the double portion of the inheritance—ultimately passed to Joseph, Reuben permanently retained the formal title of the firstborn of Israel. This enduring distinction serves several profound purposes. First and foremost, it honors Jacob. Reuben embodies the initial strength and vitality of his father, who maintained absolute purity for eighty-four years prior to this first child's birth [חומת אנך].

Beyond honoring Jacob, this title carries a deep spiritual significance connected to repairing the original sin of Adam. The three Patriarchs each played a role in rectifying the three most severe transgressions. Abraham repaired the sin of idolatry by willingly surrendering himself to the fiery furnace. Isaac repaired the sin of bloodshed by preparing to be offered as a sacrifice to God. Jacob repaired the flaw of sexual immorality through his extraordinary personal purity, a purity that culminated in the birth of Reuben. Because Jacob finalized this generational process of spiritual repair, Reuben retained the title of the firstborn as a lasting symbol of this completed mission [חומת אנך].

Finally, emphasizing Reuben's status protects the dignity of Jacob, Leah, and Reuben himself. On his wedding night, Jacob believed he was marrying Rachel. This historical detail could lead to the assumption that Reuben was conceived amidst mistaken identity and improper thoughts about another woman. However, the enduring title of the firstborn stands as a testimony to the contrary. It declares that through the righteousness and pure heart of Leah, Reuben was born entirely pure and legitimate, thereby commanding the full respect and honor worthy of a firstborn [חומת אנך].