Genesis 35:21-22

35:21 Then Israel traveled on and pitched his tent beyond Migdal Eder. ¹  35:22 While Israel was living in that land, Reuben had sexual relations with ²  Bilhah, his father’s concubine, and Israel heard about it.

Jacob had twelve sons:

[35:21]  ¹ sn The location of Migdal Eder is not given. It appears to be somewhere between Bethlehem and Hebron. Various traditions have identified it as at the shepherds’ fields near Bethlehem (the Hebrew name Migdal Eder means “tower of the flock”; see Mic 4:8) or located it near Solomon’s pools.

[35:22]  ² tn Heb “and Reuben went and lay with.” The expression “lay with” is a euphemism for having sexual intercourse.