Genesis 38:3-14 - What he did was wicked in the sight of the Lord

38:3-10

So Judah married the Canaanite Shua, and she bore him three sons: Er, Onan and Shelah. Er was the first born and Judah found a wife for him, Tamar. It is safe to assume that she was a Canaanite. Er was wicked and the Lord put him to death. We are not given any details of his sins, nor of how he died. In order to maintain the family line from the firstborn, Onan was instructed to marry Tamar. Later this would be part of the Law (Deut 25:5), but it seems to have been an established practice long before that. However, Onan would be concerned about his own family line. So it seems he enjoyed having sex with Tamar, but made sure no children resulted from it. This was considered wicked by the Lord and he too died.

38:11-14

Judah’s plan for Tamar was that she remain as a widow in her father’s house until Shelah was able to be her husband. Judah was afraid that Shelah would die like his brothers. Now we don’t know if Judah knew why Er and Onan had died. Anyway, Tamar followed Judah’s instructions. Judah’s wife died. After the time of mourning Judah went to stay with his friend Hirah in Timnah. Tamar thinks that Judah has forgotten her as he has not given Shelah to her as a husband. So she goes up to Timnah as well, aiming to meet Judah.