Genesis 35:22-24 New Revised Standard Version, Anglicised (NRSVA)
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. 24 The sons of Rachel: Joseph and Benjamin.