Genesis 38:11

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.

For he said, Lest peradventure he die also. Shelah, his third son being yet a mere boy, Judah recommended Tamar to seclude herself as a widow for a time, until that youth should have attained a marriageable age, when, as the next representative of his oldest brother, he would espouse her. But this counsel was a mere pretext to gain time. Judah was not sincere in his intentions to fulfill the promise; for, entertaining some suspicion, or cherishing a superstitious notion that marriage with Tamar was an ill-omened connection, he was secretly desirous of preventing Shelah from marrying her, and thereby saving that son from the dreaded fate of his two brothers.

But it was Judah's duty, if he did not contemplate marrying her to his son to release her from her obligation to wait for Shelah, by giving her in marriage to some other person. Judah's wife having died, the intervention of the usual mourning season of course excluded thoughts of a new family connection for a time. But that period had terminated, and the mention of it seems expressly designed to show that Judah was in circumstances to perform a father-in-law's duty to Tamar, and yet had neglected to do it.