Genesis 35:21-23 Darby Translation (DARBY)
21 And Israel journeyed, and spread his tent on the other side of Migdal-Eder.
22 And it came to pass when Israel dwelt in that land, that Reuben went and lay with Bilhah, his father's concubine; and Israel heard of it. And the sons of Jacob were twelve.
23 The sons of Leah: Reuben—Jacob's firstborn—and Simeon, and Levi, and Judah, and Issachar, and Zebulun.