The second twin pushes his way out ahead of the first, and Tamar — or, in some readings, the midwife — speaks words that the Targum Pseudo-Jonathan hears as prophecy. With what great power hast thou prevailed, and for thee will it be to prevail; for thou wilt possess the kingdom. And she called his name Pharets (Genesis 38:29). Perez — Peretz, the one who breaks through.
Pseudo-Jonathan's reading is remarkable. It does not treat this as a midwife's exclamation at a surprising birth. It treats it as an oracle. For thou wilt possess the kingdom — malkhuta, royalty. The Targum is naming, at the very moment of birth, that the line of the kings of Israel has just entered the world.
The genealogy at the end of Ruth (Ruth 4:18-22) confirms what the Targum already hears here. Perez begets Hezron, who begets Ram, who begets Amminadab, who begets Nachshon, who begets Salmon, who begets Boaz, who begets Obed, who begets Jesse, who begets David — ten generations from the child breaking out at this pyre-side birth to the king on the throne in Jerusalem. The Messiah, in rabbinic tradition, is ben Perez, the son of this one who breaks through.
The Sages hear the word peretz as the program of the entire Davidic line. Kings and the Messiah break through — fences of expectation, ordinary birth order, the verdict that seemed fixed. They arrive from places nobody was watching: from an accused widow, from a field in Moab (Ruth), from the youngest son of a shepherd in Bethlehem.
The takeaway is bracing. The power we thought we were watching for often announces itself from the opposite direction, through the one nobody had labeled first. The scarlet thread was on the other hand. The kingdom came through the brother who pushed past it.