Genesis 38:12-15

And in process of time the daughter of Shuah Judah's wife died; and Judah was comforted, and went up unto his sheepshearers to Timnath, he and his friend Hirah the Adullamite. And it was told Tamar, saying, Behold thy father in law goeth up to Timnath to shear his sheep. And she put her widow's garments off from her, and covered her with a vail, and wrapped herself, and sat in an open place, which is by the way to Timnath; for she saw that Shelah was grown, and she was not given unto him to wife. When Judah saw her, he thought her to be an harlot; because she had covered her face.