Charles Ellicott Commentary Genesis 38:11

"Then said Judah to Tamar his daughter-in-law, Remain a widow in thy father`s house, till Shelah my son be grown up; for he said, Lest he also die, like his brethren. And Tamar went and dwelt in her father`s house." — Genesis 38:11 (ASV)

For he said, lest he also die.—It is evident from this that Judah, for reasons which, in Genesis 38:26, he acknowledged to be insufficient, wished to evade the duty of giving a third son to Tamar. It does not follow that he blamed her for their deaths, for the loss of two sons in succession might well frighten him.

Philippsohn says that it became the rule, that if a woman lost two husbands, the third brother was not bound to marry her, and she was even called Katlannith. the murderess. (But see Matthew 22:25-26, where no such custom is acknowledged.)