Why Did God Kill Onan? (Bible and Contraception)

Why Did God Kill Onan? (Bible and Contraception) December 31, 2019

Genesis 38:9-10: “But Onan knew that the offspring would not be his; so when he went in to his brother’s wife he spilled the semen on the ground, lest he should give offspring to his brother. 10 And what he did was displeasing in the sight of the Lord, and he slew him also.”

It is an historical fact that no Christian communion sanctioned contraception until the Anglican Lambeth Conference in 1930. Protestant historian Roland Bainton states casually that the Church “very early forbade contraception” (Early Christianity, 56). According to The Oxford Dictionary of the Christian Church, “many Christian moralists . . . repudiate all methods of family limitation” (Cross, 889). Ronald Knox eloquently recounted how Christians used to detest contraception:

Practices hitherto connected with the unmentioned underworld have found their way into the home . . . it is not merely a Christian principle that has been thrown overboard . . . Ovid and Juvenal, with no flicker of Christian revelation to guide them, branded the practices in question with the protest of heathen satire. It is not Christian morality, but natural morality as hitherto conceived, that has been outraged by the change of standard. (Knox, 31-32)

Christianity (Catholicism, Orthodoxy, and Protestantism alike) had always opposed contraception as gravely sinful. When I first learned of this in 1990 (as an inquiring evangelical pro-life activist curious about the “odd” and inexplicable Catholic prohibition) it was a shocking revelation to me and the first step on my road to conversion to Catholicism.

Today, probably upwards of 90% of Protestants and 80% of Catholics use contraceptives. It is a mortal sin in Catholicism, and used to always be considered an extremely serious sin in Protestant circles. How things change. The great Anglican apologist C. S. Lewis, for example, opposed contraception:

As regards contraceptives, there is a paradoxical, negative sense in which all possible future generations are the patients or subjects of a power wielded by those already alive. By contraception simply, they are denied existence; by contraception used as a means of selective breeding, they are, without their concurring voice, made to be what one generation, for its own reasons, may choose to prefer. From this point of view, what we call Man’s power over Nature turns out to be a power exercised by some men over other men with Nature as its instrument. (The Abolition of Man, 68-69)

Genesis 38:9-10 (about Onan) has been one of the main prooftexts traditionally used to oppose contraception. Observe how Martin Luther interpreted this biblical passage:

Onan must have been a malicious and incorrigible scoundrel. This is a most disgraceful sin. It is far more atrocious than incest and adultery. We call it unchastity, yes, a Sodomitic sin. For Onan goes in to her; that is, he lies with her and copulates, and when it comes to the point of insemination, spills the semen, lest the woman conceive. Surely at such a time the order of nature established by God in procreation should be followed . . . He was inflamed with the basest spite and hatred . . . Consequently, he deserved to be killed by God. He committed an evil deed. Therefore God punished him . . . That worthless fellow . . . preferred polluting himself with a most disgraceful sin to raising up offspring for his brother. (Lectures on Genesis: Chapters 38-44; 1544; LW, 7, 20-21)

John Calvin, in his Commentary on Genesis is no less vehemently opposed to the practice (what would he think if he knew about the vast majority of Calvinists today who regularly contracept?):

I will contend myself with briefly mentioning this, as far as the sense of shame allows to discuss it. It is a horrible thing to pour out seed besides the intercourse of man and woman. Deliberately avoiding the intercourse, so that the seed drops on the ground, is double horrible. For this means that one quenches the hope of his family, and kills the son, which could be expected, before he is born. This wickedness is now as severely as is possible condemned by the Spirit, through Moses, that Onan, as it were, through a violent and untimely birth, tore away the seed of his brother out the womb, and as cruel as shamefully has thrown on the earth. Moreover he thus has, as much as was in his power, tried to destroy a part of the human race. When a woman in some way drives away the seed out the womb, through aids, then this is rightly seen as an unforgivable crime. Onan was guilty of a similar crime, by defiling the earth with his seed, so that Tamar would not receive a future inheritor.

The New Bible Dictionary concludes, on the other hand, “this verse does not pass any judgment on birth control as such” (Douglas, 789). The reasoning often used to overcome the force of the verse is that Onan was punished by God (with death) for disobeying the “levirate law,” whereby a brother of a dead husband was to take his sister-in-law as his wife and have children with her (Deuteronomy 25:5-10).

But that can’t apply in this case (or any other) because the same work informs us that the law “allows the brother the option of refusing.” Thus we find in Deuteronomy 25:9 that a sister-in-law so refused should “spit in his face,” but there is no mention of any death penalty or the wrath of God.

How then, can the New Bible Dictionary be so sure that the slaying of Onan by God had no relation to contraception? God didn’t command Onan in this case – another argument sometimes heard — , so he wasn’t directly disobeying God (it was his father Judah who asked him to do what he didn’t want to do: Gen 38:8).

Whatever was “displeasing” to God couldn’t have been disobedience regarding the levirate law, since He allowed people to disobey it and recommended that they suffer only public humiliation, not death, which is not nearly as serious as being “wicked” — the reason God slew Onan’s brother Er (Gen 38:7).

Moreover, the passage which teaches about the levirate law (Deuteronomy 25:5-10) is from God, as part of the covenant and the Law received by Moses on Mt. Sinai, and proclaimed by Him to all of Israel (see Deut 5:1-5, 29:1, 12).

If God Himself did not say that the punishment for disobeying the levirate law was death (in the place where it would be expected if it were true), how can modern commentators “know” this? Can it be that their “knowledge” exists in order to avoid uncomfortable implications concerning a prohibition of contraception? Might there be a little bit of bias at play?

Yet the article on Onan in the same dictionary (the earlier comment was in the article, “Marriage”), written by the editor, J. D. Douglas, states:

Onan . . . took steps to avoid a full consummation of the union, thus displeasing the Lord, who slew him. (Douglas, 910)

Douglas appears to contend that Onan was killed for the contraceptive act, not disobedience to the levirate law. If so, his opinion contradicts the view expressed in the other article by J. S. Wright and J. A. Thompson. The Eerdmans Bible Dictionary concurs:

. . . whenever Onan and Tamar had intercourse he would spill his sperm on the ground to prevent her from conceiving; for this the Lord slew him.

Onan’s tactic of withdrawing before ejaculation . . . costs him his life. (Myers, 781, 653)

In its article on “Levirate Law,” we are also informed that “the brother had the option of refusing to take his sister-in-law in levirate marriage (652). The logic is apparent: if refusal alone was not grounds to be killed by God or by capital punishment issued by his fellows, then there must have been something in the way Onan refused which was the cause. This was the “withdrawal method,” a form of contraception (probably the one most used throughout history). Therefore, Onan was killed for doing that, which in turn means that God didn’t approve of it.

One might still retort as follows: “it is not contraception per se that was wrong in Onan’s case, but the fact that he wanted to have sex with the woman but not to have children. He had the right to refuse the levirate marriage, but once he agreed to it he was obligated to produce the children which was the purpose of it.”

I would agree with this hypothetical objection prima facie, but (upon closer inspection) I would add that it actually confirms the central moral point on which the moral objection to contraception is based: the evil of separating sex from procreation. It is precisely because the central purpose of marriage is procreation, that the levirate law was present in the first place. If one married, they were to have sexual relations, which was (foremost) for the purpose of having children.

If a husband died with no children, it was so important for children to be born that God commanded the man’s brother to take his wife after he died. But Onan tried to separate sex from procreation. He wanted all the pleasure but not the responsibility of fatherhood or to help perpetuate his brother’s family. He possessed the “contraceptive mentality” which is rampant today, even among otherwise traditional, committed Christians.

This is what is evil: an unnatural separation of what God intended to be together. If Onan didn’t want children, he shouldn’t have agreed to the levirate marriage. Once married, he should have agreed to having children. But he tried the “middle way” of having sex but willfully separating procreation from it. This was the sin, and this is why God killed him. Martin Luther understood the fundamental evil of contraception and the “anti-child” mindset:

Today you find many people who do not want to have children. Moreover, this callousness and inhuman attitude, which is worse than barbarous, is met with chiefly among the nobility and princes, who often refrain from marriage for this one single reason, that they might have no offspring. It is even more disgraceful that you find princes who allow themselves to be forced not to marry, for fear that the members of their house would increase beyond a definite limit. Surely such men deserve that their memory be blotted out from the land of the living. Who is there who would not detest these swinish monsters? But these facts, too, serve to emphasize original sin. Otherwise we would marvel at procreation as the greatest work of God, and as a most outstanding gift we would honor it with the praises it deserves. (Lectures on Genesis: Chapters 1-5, 1536; LW, I, 118; commentary on Genesis 2:18)

The rest of the populace is more wicked than even the heathen themselves. For most married people do not desire offspring. Indeed, they turn away from it and consider it better to live without children, because they are poor and do not have the means with which to support a household. . . . But the purpose of marriage is not to have pleasure and to be idle but to procreate and bring up children, to support a household. . . . Those who have no love for children are swine, stocks, and logs unworthy of being called men and women; for they despise the blessing of God, the Creator and Author of marriage. (Lectures on Genesis: Chapters 26-30; LW, V, 325-328; vol. 28, 279; commentary on the birth of Joseph to Jacob and Rachel; cf. LW, vol. 45, 39-40)

But the greatest good in married life, that which makes all suffering and labor worth while, is that God grants offspring and commands that they be brought up to worship and serve him. In all the world this is the noblest and most precious work, because to God there can be nothing dearer than the salvation of souls. Now since we are all duty bound to suffer death, if need be, that we might bring a single soul to God, you can see how rich the estate of marriage is in good works. (The Estate of Marriage, 1522; LW, vol. 45, 46)

You will find many to whom a large number of children is unwelcome, as though marriage had been instituted only for bestial pleasures and not also for the very valuable work by which we serve God and men when we train and educate the children whom God has given us. They do not appreciate the most pleasant feature of marriage. For what exceeds the love of children? (In Plass, II, #2834)

Let’s examine more traditional Protestant commentary on Genesis 38:8-9. Matthew Henry decries “the great abuse of his own body” and “sins that dishonour the body and defile it” which “are very displeasing to God and evidences of vile affections.” John Wesley actually quotes Henry, adds that Onan was abusing his wife, and concludes with this powerful condemnation:

Observe, the thing which he did displeased the Lord — And it is to be feared, thousands, especially of single persons, by this very thing, still displease the Lord, and destroy their own souls.


Bainton, Roland H., Early Christianity, New York: D. Van Nostrand Company, 1960.

Calvin, John, Calvin’s Commentaries, 22 volumes, translated and edited by John Owen; originally printed for the Calvin Translation Society, Edinburgh, Scotland, 1853; reprinted by Baker Book House, Grand Rapids, Michigan: 1979. Available online: http://www.ccel.org/c/calvin/comment2/

Cross, F. L. and E. A. Livingstone, editors, The Oxford Dictionary of the Christian Church, Oxford: Oxford University Press, 2nd edition, 1983.

Douglas, J. D., editor, The New Bible Dictionary, Grand Rapids, Michigan: Eerdmans Pub. Co., 1962.

Henry, Matthew [Presbyterian], Complete Commentary on the Whole Bible, 1706. Available online:

Knox, Ronald, The Belief of Catholics, Garden City, New York: Doubleday Image, 1927; reprinted in 1958.

Lewis, C. S., The Abolition of Man, New York: Macmillan, 1947.

Luther, Martin, Luther’s Works (LW), American edition, edited by Jaroslav Pelikan (volumes 1-30) and Helmut T. Lehmann (volumes 31-55), St. Louis: Concordia Pub. House (volumes 1-30); Philadelphia: Fortress Press (volumes 31-55), 1955.

Myers, Allen C., editor, The Eerdmans Bible Dictionary, Grand Rapids, Michigan: Eerdmans, 1987; English revision of Bijbelse Encyclopedie, edited by W. H. Gispen, Kampen, Netherlands: J. H. Kok, revised edition, 1975; translated by Raymond C. Togtman and Ralph W. Vunderink.

Plass, Ewald M., What Luther Says, an Anthology, two volumes, St. Louis: Concordia Publishing House, 1959.

Wesley, John [founder of Methodism], Explanatory Notes on the Whole Bible, 1765. Available (online):

* * * * *

From my book: The Catholic Verses: 95 Bible Passages That Confound Protestants (published in 2004 by Sophia Institute Press)

For further fascinating exegesis of the Onan passage, see Fr. Brian Harrison’s comments: “The Sin of Onanism Revisited.”


Related Reading:

Dialogue: Why Did God Kill Onan? (Contraception) [2-13-04]

Onan, Contraception, & Two Protestant Bible Dictionaries [2-21-04]

Biblical Data Against Contraception: Onan’s Sin and Punishment: a Concise “Catholic” Argument  [3-7-14]

Bible vs. Contraception: Onan’s Sin and Punishment [National Catholic Register, 5-30-17]

Dialogue w Several Non-Catholics on Contraception [1996 and 1998]

Contraception: Early Church Teaching (William Klimon) [1998]

Dialogue: Contraception vs. NFP: Crucial Ethical Distinctions [2-16-01]

Luther and Calvin Opposed Contraception and “Fewer Children is Better” Thinking [2-21-04; published at National Catholic Register, 9-13-17]

Biblical Evidence Against Contraception [5-3-06]

Dialogue: Contraception & Natural Family Planning (NFP) [5-16-06]

“Divine Family Planning” (Unlimited Children / Anti-NFP): Critique [9-20-08]

Bible on the Blessing of [Many] Children [3-9-09]

Natural Family Planning (NFP) & “Contraceptive Intent” [8-28-13]

Contraception and “Anti-Procreation” vs. Scripture [National Catholic Register, 6-6-18]

A Defense of Natural Family Planning [National Catholic Register, 5-25-19]


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(originally 2-9-04)

Photo credit: Judah and Tamar (anon., Italian, 17th c.) [public domain / Wikimedia Commons]


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