Genesis 35:21-23 Common English Bible (CEB)
21 Israel continued his trip and pitched his tent farther on near the tower of Eder.
22 While Israel stayed in that place, Reuben went and slept with Bilhah his father’s secondary wife, and Israel heard about it.
Jacob had twelve sons. 23 The sons of Leah were Reuben, Jacob’s oldest son, and Simeon, Levi, Judah, Issachar, and Zebulun.