Why God Killed Onan

The biblical story of Onan in Genesis 38.6–11 is one that has traditionally been used by Christians, especially Catholics, to show that God detests contraceptive sex and masturbation, or at least male masturbation (since the loss of sperm leads to loss of life, i.e. loss of a substance with the potential to produce offspring). Not just masturbation accompanied by sexual fantasy, visual aids, etc., but any self-stimulation of one's genitalia without reproduction as its end goal. But I'm partial to another interpretation of the biblical text, one that Catholic Answers says has become the orthodoxy in contemporary biblical exegesis. According to this standard interpretation, Onan's sin was failing to perform his duty to impregnate his widowed sister-in-law—nothing more, nothing less. This Israelite practice that Onan failed to follow was known as levirate marriage. Had Onan's brother not died, Onan could have engaged in as much masturbation and contraceptive sex as he pleased, more or less.

The question arises: given that the punishment in Jewish law for noncompliance with the levirate marriage custom was mere public humiliation,¹ why did God punish Onan's behavior so much more severely, putting Onan to death? Catholics answer that it's because Onan not only failed to comply with levirate marriage but, while in bed with Tamar, either masturbated or pulled out, thereby frustrating the proper function of his genitalia: making babies.² Note that, even if this is why God killed Onan, it doesn't mean that God thought death was a proper punishment for any contraceptive sex or masturbation whatsoever. Perhaps Onan only deserved death due to the cumulative sinfulness of the withdrawal method of contraception and noncompliance with levirate marriage.

That said, I propose an alternative explanation, namely that Onan's noncompliance with levirate marriage was particularly bad in God's eyes (and not specifically because Onan used coitus interruptus). Observe that, of all the 12 tribes of Isreal, the tribe descended from Judah was the greatest. It was the most populous and powerful, it absorbed the tribe of Benjamin, it gave rise to great kings like David and Solomon, and it's the tribe from which a hefty majority of modern-day Jews believe they descended. Most importantly, prophets foretold that the Davidic lineage from Judah would give rise to a messiah (mashiach),³ a king who would save God's chosen people—the Jews—by "deliver[ing] Israel from foreign bondage and restor[ing] the glories of its golden age."⁴ Observe further that Onan and his deceased brother Er were Judah's sons, and Tamar was Er's wife. Judah only had a few descendants at the time, so the lineage could've easily died out if those descendants didn't get busy reproducing. The growth of the tribe of Judah, which was surely a central part of God's plan for humanity, was already jeopardized by Er's death. So then when Onan failed to impregnate Tamar, the problem was exacerbated. Not every instance of noncompliance with levirate marriage risked foiling God's plan as thoroughly as this, for not every levirate marriage would've contributed or had the potential to contribute to the development of a great tribe. And only God would be in a position to know whether such a great tribe would result from the continuation of a given lineage; as such, unless God told them, humans could never say for sure that a given case of breaking levirate marriage law warranted more severe punishment than humiliation. Thus, it makes sense that humans would only carry out the minimum punishment that any violation of the levirate marriage custom was thought to deserve, and that the responsibility of punishing the more egregious violations would be left to God.

What I said above is arguably sufficient to explain God's wrath. But one additional mistake that Onan made, compounding the seriousness of his sin, was that he got jealous. The passage explicitly states that he refused to impregnate Tamar because the children would be (customarily regarded as) his brother's, not his own. Envy is one of the seven deadly sins, and the Ten Commandments famously ban covetousness along with murder, adultery, and such. So this was no minor error on Onan's part. And although such envy was probably a common reason that Jews disregarded the levirate marriage custom, they could've disregarded it without being envious, in which case public humiliation might have been punishment enough.

Endnotes

1. Deuteronomy 25.7–10 (NRSV): But if the man has no desire to marry his brother’s widow, then his brother’s widow shall go up to the elders at the gate and say, “My husband’s brother refuses to perpetuate his brother’s name in Israel; he will not perform the duty of a husband’s brother to me.” Then the elders of his town shall summon him and speak to him. If he persists, saying, “I have no desire to marry her,” then his brother’s wife shall go up to him in the presence of the elders, pull his sandal off his foot, spit in his face, and declare, “This is what is done to the man who does not build up his brother’s house.” Throughout Israel his family shall be known as “the house of him whose sandal was pulled off.”

2. Source: https://www.catholic.com/magazine/print-edition/the-real-sin-of-onan

3. Source: https://www.britannica.com/topic/Judah-Hebrew-tribe

4. Source: https://www.britannica.com/topic/messiah-religion