Overview
Onan was the son of Judah and appears in Genesis 38 during the account of Judah and Tamar. When his older brother Er died without children, Onan was commanded by custom and law to marry Tamar and produce an heir for his brother's name. However, Onan refused this responsibility and was struck down by the Lord for his disobedience.
Key Scriptures
"Then Judah said to Onan, 'Go in to your brother's wife and perform the duty of a brother-in-law to her, and raise up offspring for your brother'" (Genesis 38:8, ESV).
"But Onan knew that the offspring would not be his. So whenever he went in to his brother's wife he would waste the semen on the ground, so as not to give offspring to his brother" (Genesis 38:9, ESV).
"And the Lord put him to death also" (Genesis 38:10, ESV).
Application
Onan's account warns against selfish disobedience to clear biblical commands and the importance of fulfilling our responsibilities to family and God's established order.