Genesis 35:21-23 English Standard Version Anglicised (ESVUK)
21 Israel journeyed on and pitched his tent beyond the tower of Eder.
22 While Israel lived in that land, Reuben went and lay with Bilhah his father's concubine. And Israel heard of it.
Now the sons of Jacob were twelve. 23 The sons of Leah: Reuben (Jacob's firstborn), Simeon, Levi, Judah, Issachar, and Zebulun.