Judah said to Onan, “Go and sleep with your brother’s wife — perform the duty of a husband’s brother to her, and preserve your brother’s line of descent.”-Genesis 38:8
For those who are relatively new to the ancient world of the Old Testament, I need to go over a custom known as “Levirate Marriage”.
This practice is spelled out in Deuteronomy 25:5-10.
The original Hebrew word for this ordinance is YIBBUM.
In a nutshell, if a man dies childless, his brother is obligated to marry his widow and her first son is reckoned as the offspring of the deceased.
However, the surviving brother can decline and undergo a procedure that the rabbis named “halitzah“.
You should know that a form of Levirate marriage existed in other cultures as well.
Testimony of this practice can be found in ancient Hittite writings and preserved documents from the Middle Assyrian age.
So in accordance with this custom, Judah commanded Onan to fulfill his duty to his deceased brother.
But Onan only half-obeyed because while he married Tamar, he refused to impregnate her.
The reason given us in Scripture is because “Onan knew that the child would not be his“.
Why did this bother Onan so much?
If Onan created a child in the name of his deceased brother, that child would have been eligible to receive a substantial portion of Judah’s estate.
This substantial portion is what Onan would have failed to acquire for himself.
In addition, if a widow in those times failed to give birth to a son, it would result in the following two things:
1) Her deceased husband’s family line would perish! This was an unspeakable disaster to the ancient mind.
2) She would have nobody to take of her in her old age.
What Onan did was not just selfish, it was an extremely cold-hearted act.
And God killed him for it.
One final point before I close.
Given the similarity in spelling and pronunciation, one might jump to the conclusion that Levirate marriage is somehow related the to the Tribe of Levi.
However, there is no connection and the similarity is pure coincidence.
The word “Levirate” actually comes from the Latin word “levir” meaning “a husband’s brother“.