Genesis 38:11

Shelah was not yet old enough to have sex with Tamar. When Shelah was older, he would have the duty of the husband’s brother. He would have a duty to produce a son for his dead brother Er. So Tamar waited until Shelah was older. But Judah did not intend to let Shelah do his duty. Judah was afraid that Shelah might die. (See the comment on verse 14.)

v12 After a long time Judah’s wife, who was Shua’s daughter, died. Judah wept for her for a time. After that time, he went to Timnah, where his servants were cutting the wool from his sheep. He went there with his friend Hirah the Adullamite.

v13 People said to Tamar, ‘Your husband’s father goes to Timnah. There they are cutting the wool from his sheep.’ v14 Tamar had realised that Shelah had become a man. And he had not taken her as a wife. So she took off her widow’s clothes and she covered her face. She put perfume on herself. Then she sat at the gate to Enaim, which is on the way to Timnah.