Genesis 35:21-23 Christian Standard Bible (CSB)
21 Israel set out again and pitched his tent beyond the Tower of Eder.[a] 22 While Israel was living in that region, Reuben went in and slept with his father’s concubine Bilhah, and Israel heard about it.
Jacob had twelve sons:
23 Leah’s sons were Reuben (Jacob’s firstborn),
Simeon, Levi, Judah,
Issachar, and Zebulun.