1And it came to pass at that time, that Judah went down from his brethren, and turned in to a certain Adullamite, whose name was Hirah.

2 And Judah saw there a daughter of a certain Canaanite, whose name was Shuah; and he took her, and went in unto her.

3 And she conceived, and bare a son; and he called his name Er.

4 And she conceived again, and bare a son; and she called his name Onan.

5 And she yet again conceived, and bare a son; and called his name Shelah: and he was at Chezib, when she bare him.

6 And Judah took a wife for Er his firstborn, whose name was Tamar.

7 And Er, Judah's firstborn, was wicked in the sight of the Lord; and the Lord slew him.

8 And Judah said unto Onan, Go in unto thy brother's wife, and marry her, and raise up seed to thy brother.

9 And Onan knew that the seed should not be his; and it came to pass, when he went in unto his brother's wife, that he spilled it on the ground, lest that he should give seed to his brother.

10 And the thing which he did displeased the Lord: wherefore he slew him also.

11 Then said Judah to Tamar his daughter in law, Remain a widow at thy father's house, till Shelah my son be grown: for he said, Lest peradventure he die also, as his brethren did. And Tamar went and dwelt in her father's house.

12 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.

Source: Bible, excerpts copied from the International Bible Society
https://www.biblica.com/bible/kjv/genesis/38/

SUMMARY OF THE REMAINING OF THE CHAPTER:

She had to take off her widow's outfit.

Tamar would have to wait for her father-in-law to keep the promise. But her father-in-law was going through a path on which Tamar put herself disguised as a prostitute

Tamar's mother-in-law had lost his wife. Passing Tamar on the way, and told her if she did not want to lie with him. She asked as payment her two objects. After three months Tamar's pregnancy became apparent. His father-in-law learned about the pregnancy and sent for Tamar. She sent the objects and her father-in-law recognized them. He never slept with her again. The father-in-law claims that she was more righteous than he, for he had not kept the promise that made her to marry her with her other son.