Start with the name, because in this family the names are never decoration — they're prayers, or wounds, spoken out loud at the moment of birth. Leah, Jacob's unloved wife, has her first son and names him Reuben — "see, a son," or more fully, "the LORD hath looked upon my affliction" (Genesis 29:32). Notice what she's actually saying: not gratitude for a child so much as a hope, spoken half to herself, that this son will finally make her husband love her. It doesn't work. She'll say something almost identical after her next two sons, and it still doesn't work. Hold that ache in the background as you read everything else about this family, because it's the engine running underneath most of what goes wrong between the brothers later.
Reuben is the firstborn, which in the ancient world meant something concrete — a double portion of inheritance, positional authority, the family's future resting on his shoulders. And he throws it away with a single act recorded in one blunt verse: "Israel... went and lay with Bilhah his father's concubine: and Israel heard it" (Genesis 35:22). Genesis doesn't dramatize the moment or explain the motive. It just states it and moves on, the way it states Sarah's barrenness plainly back in chapter eleven — a fact, without commentary, left to do its own damage later.
And it does. When Jacob gathers his sons on his deathbed to speak over each of them in turn, Reuben is first, and the blessing turns immediately into an indictment: "Reuben, thou art my firstborn, my might, and the beginning of my strength, the excellency of dignity, and the excellency of power: unstable as water, thou shalt not excel; because thou wentest up to thy father's bed" (Genesis 49:3–4). Watch the shape of that sentence — every clause building up what Reuben should have been, and then one final clause taking it all back. "Unstable as water" isn't just a character note. It's the reason the tribe of Reuben settles quietly east of the Jordan (Numbers 32) and produces no judge, no king, nothing the rest of the Old Testament particularly remembers.
But don't let the curse be the last word before you've noticed the one moment that complicates it. When the brothers plot to kill Joseph outright, it's Reuben who talks them down — "let us not kill him... shed no blood, but cast him into this pit" — and the text tells you plainly why: "that he might rid him out of their hands, to deliver him to his father again" (Genesis 37:21–22). It's a quiet, largely failed rescue attempt — he comes back to the pit later and Joseph is already gone, sold — but it's real. The unstable man still had it in him to try to do the right thing when it mattered.
That's worth carrying with you longer than the curse is. Reuben lost the birthright through one specific failure, and Scripture doesn't pretend otherwise. But it also doesn't reduce him to that failure alone — the same man who couldn't hold his position also couldn't quite bring himself to let his brother die. Instability cuts both ways: it's what loses you what you were given, and it's also, sometimes, what leaves just enough conscience intact to try to do better when it counts.