Targum Pseudo-Jonathan preserves one of the strangest accounts in all of Jewish tradition (Genesis 32:25). Jacob was left alone across the Jabbok, and an angel wrestled him in the form of a man. But what were they fighting about?
The Targum answers: the angel was Michael, and he had come with an accusation. "Did you not promise to give a tenth of everything that is yours? And behold, you have ten sons and one daughter — and yet you have not tithed them."
Jacob, confronted, did the math in the middle of a fight. The rabbis imagined it vividly. He set aside the four firstborn of his four mothers (Reuben, Dan, Gad, Joseph), because firstborns already belong to God and cannot count toward a tithe. That left eight. He began counting from Simeon — and Levi came up as the tenth.
Why Levi
Michael then declared: "Lord of the world, this is Your lot." Levi, selected by the turning of the count, became the tribe of priests. The Targum says Michael stayed by the torrent until the dawn column arose, escorting the tithed son into his destiny.
The takeaway: what Jacob promised at Bethel came due at the Jabbok. Every vow has its reckoning, and every tribe of Israel began with one.