*** Caveat ***
Onan's sin was something disgusting, something that displeased God, and for which Onan was slain. The reason I'm spending a whole post on this topic is that recently some Roman Catholics have been trying to use the issue of Onan's sin as some sort of argument that "Protestant" folks are unwilling to consider Scripture.
I realize, as well, that there are some Roman Catholics for whom this is not a matter of serious consideration. They have a theology that their church has given them (or so they think) and they are going to stick with that, regardless of what Scripture says or doesn't say.
I also realize that some of them think that it is a notable matter that many of the Reformers held over some traditional ideas that influenced their view of what Onan's sin was. Apparently, for them, it is a significant issue if our understanding of the text is different than the majority view of the text from relatively early in the patristic period through at least the first two centuries of the Reformation era.
Finally, of course, I've tried to use euphemism in the following discussion, for reasons that should be apparent to any adult. If you decide to comment on this post, keep in mind that if your comments are explicit, I will censor them.
*** End of Caveat ***
What is the sin of Onan? Many Roman Catholics today argue against certain contraceptive activities on, among other things, the idea that this is condemned as the sin of Onan in Genesis 38:9. The following is a response to that idea.
First, the text:
Genesis 38:9 And Onan knew that the seed should not be his; and it came to pass, when he went in unto his brother's wife, that he spilled it on the ground, lest that he should give seed to his brother.
Next, the text in context:
And Judah took a wife for Er his firstborn, whose name was Tamar. And Er, Judah's firstborn, was wicked in the sight of the LORD; and the LORD slew him. And Judah said unto Onan, Go in unto thy brother's wife, and marry her, and raise up seed to thy brother. And Onan knew that the seed should not be his; and it came to pass, when he went in unto his brother's wife, that he spilled it on the ground, lest that he should give seed to his brother. And the thing which he did displeased the LORD: wherefore he slew him also. Then said Judah to Tamar his daughter in law, Remain a widow at thy father's house, till Shelah my son be grown: for he said, Lest peradventure he die also, as his brethren did. And Tamar went and dwelt in her father's house.
i) Genesis 38:9 does not provide any universal moral commandment.
The wording of the verse itself should be a clue to that. Also, of course, the context of the verse should be a clue. The verse is worded in that God was displeased by what Onan did and slew Onan. Furthermore, this discussion is not given in the context of a set of laws, but rather in the context of an historical account.
ii) Genesis 38:9 is susceptible to several possible interpretations, because it merely states that the thing that Onan did displeased God and that consequently God slew him.
There are several possible things that displeased God about what Onan did. The thing that displeased God could be:
1) Because Onan slept with his brother's widow.
2) Because Onan spilled his seed on the ground.
3) Because Onan refused to raise up seed to his brother.
4) Because Onan disobeyed his father.
We can rule out (1), because Judah had commanded Onan to do this, and Judah's command is supported by the later Mosaic codification of the levirate law (Deuteronomy 25:5-10).
If (2) is correct (and, in a sense, it is correct), the question is why? The only clear answer is ...
That (3) is correct. The reason that spilling the seed on the ground was wrong was because it was a refusal to perform the duty required by Judah and later codified by Moses. Onan failed to honor his father, and God slew him.
We might add (4) as well, but (4) is correct inasmuch as (3) is correct.
iii) Several less general principles can be drawn from this passage.
It is dangerous to rush to generalizations from a single passage. There are several generalizations that could be made from this text, in view of the meaning of the text.
1) That disobedience to parents is wrong.
2) That failure to obey the levirate law is wrong.
3) That levirate relations should be procreative only.
4) That marital relations should be procreative only.
Given the level of detail provided in the text, (1) seems to be unsatisfying. It does not seem that God was simply displeased because Onan disobeyed his father, but over the manner in which he did so.
The fourth option (4) is much too general. The fact that this was a levirate relationship is significant to the flow of the text, and a generalization that fails to account for this seems to fail to identify the true issue.
The remaining options are (2) and (3). These are not far apart. Nevertheless, we can distinguish between the two. The issue is not one in which Onan obeyed the levirate law and then did something else in addition, instead it is one in which he refused to obey the levirate law. Thus, (2) is the better answer than (3).
iv) The fact that Calvin (and Luther?) viewed Onan's activity to be inherently displeasing to God does not make it so.
A surprising number of people think that it is significant that Luther (?) and Calvin generalized Onan's sin rather differently than we do. Nevertheless, Luther and Calvin agreed with us that their views ought to be held up to the light of Scripture. Since their views of this particular text do not seem to be sustainable exegetically, we are justified in departing from their position on this issue.
Some have even gone so far as to suggest that if we say Luther/Calvin/whoever misunderstood this text, we're saying they were unsaved. Certainly that is not what we are saying. The fact that people disagree with the best exegesis of the text does not mean that those people are not Christians.
v) Does Onan's intent matter?
In seeking to generalize the teaching of the verse differently, some have asserted that Onan's intent in doing what he did was unimportant. It didn't really matter (say they) that he was seeking to avoiding raising up children to his brother. I find this idea strange. Intent is normally highly significant. Furthermore, the text makes a point of telling us Onan's intent.
If we ignore Onan's intent, we would be in the position of saying that even if Onan simply spilled it accidentally, God would still have slain him and that Scripture uselessly provided us with this information about what was going on inside Onan's mind. Can any reasonable person think that is the case?
vi) What about Er?
Note that Er was also wicked and was slain by God. We're not told what Er did, and yet we know Er didn't have children. Some have interpolated this to mean that Er was doing the same basic act as what Onan was doing, and have attempted to use this to justify generalizing beyond the levirate situation.
The problem with such a claim is that the extent of our knowledge is that Onan's older brother Er was wicked and was slain by God. We're not told why or what he did. We are not told that he did anything remotely similar to what Onan did. Furthermore, Judah's concern regarding Shelah does not seem to be motivated by a fear that he will do the same thing as Onan, but more of essentially a fear that Tamar was "bad luck."
Likewise, the larger context (which I have omitted for brevity) adds that Judah ultimately blocked Onan's younger brother from marrying Tamar (Er/Onan's widow). Subsequently, Judah himself did (unintentionally) raise up seed to his son, by sleeping with his son's widow (whom he thought at the time was a prostitute). It should be noted, however, that the children of that union are never attributed to Er, but always to Judah.
vii) But is the death penalty the appropriate punishment for violation of the levirate law?
While Moses did not appoint death for violation of the levirate law, God is free to sentence to death everyone who violates His law in any degree (James 2:10 For whosoever shall keep the whole law, and yet offend in one point, he is guilty of all.) And, in any event, dishonoring one's parents was a capital crime under Mosaic system, and the command here was a command of Onan's father.