Genesis 38:13-16

13Someone told Tamar, ‘Your husband's father is going to Timnah to get the wool from his sheep.’

14Tamar knew that Judah's son Shelah had now become a man. But Judah had not yet let Shelah marry her. So Tamar took off her widow's clothes and she put on other clothes. She covered her head with a veil. She did not want anyone to recognize her. Then she sat at the gate of Enaim. Enaim is a town on the road that goes to Timnah.

15Judah saw her as she sat there. He thought that she was a prostitute, because she had covered her face.

16He did not know that she was his son's widow. He went to her at the side of the road. He said, ‘Let me have sex with you.’ Tamar asked him, ‘If I have sex with you, what will you give me?’