Genesis 38:1-6

About that time, Judah left his brothers and went to stay with a man named Hirah in the town of Adullam. There Judah met a Canaanite girl, the daughter of a man named Shua, and married her. Judah had sexual relations with her, and she became pregnant and gave birth to a son, whom Judah named Er. Later she gave birth to another son and named him Onan. Still later she had another son and named him Shelah. She was at Kezib when this third son was born. Judah chose a girl named Tamar to be the wife of his first son Er.