Gen 38 – What is a “Levirate marriage?” Onan found out the hard way.

Gen 38:6
Now Judah took a wife for Er his first-born, and her name was Tamar.

Obviously several years have passed. The firstborn son grows up to the age of marriageability. We are not told of the meaning of her name. Nor are we told the meanings of the names of the sons of Judah, for that matter.

Gen 38:7
But Er, Judah's first-born, was evil in the sight of the LORD, so the LORD took his life.

We are not told what Er did that was so wicked. But the fact that Judah married a Canaanite woman gives us enough of a hint to know that it possibly had to do with idolatry or pagan worship of some kind. It is interesting that it does not say he "did evil in the sight of Yahweh." It says he "was evil in the sight of Yahweh." The implication is that Er's life was a wicked and lawless one. This can be attributed, at least partially, to Judah taking a pagan wife.

Gen 38:8
Then Judah said to Onan, "Go in to your brother's wife, and perform your duty as a brother-in-law to her, and raise up offspring for your brother."

Judah is speaking of the practice of what has been called "the Levirite marriage." Levirite is Latin for "husbands brother." Judah is following the law as it was undoubtedly given to him and others long before Sinia (Deut. 25:5- 6). It is the duty of the younger brother to see that his brother's name is carried on. To not do this is shameful and the offending brother is publicly disgraced (Deut. 25:7-10).

Gen 38:9
And Onan knew that the offspring would not be his; so it came about that when he went in to his brother's wife, he wasted his seed on the ground, in order not to give offspring to his brother.

Onan knew that their son would not perpetuate his name according to the law.

Deut 25:5-6
He was not only failing to provide offspring for his deceased brother, but he in doing so, he would steal his brothers inheritance. Onan was evil also, much like his brother Er. He brought the wrath of Elohim down upon himself.

Gen 38:10
But what he did was displeasing in the sight of the LORD; so He took his life also.