These verses from Genesis have been debated for thousands of years, but I can't help giving my two cents and sharing my opinion on the issue. The Bible is a fascinating book, but I often get the sense that many people try much too hard to find interpretations within minor parts of a story- in essence missing the forest for the trees. I think that happens with this passage in a fairly major way.
Note: This post does not address whether a business owner can enforce his religious ideas on his employees, that's clearly an unconstitutional horrible awful bad idea. I'm simply trying, as a Christian myself, to understand a rule that other Christians follow and consider important. And I disagree with them.
Genesis 38:8-10 (KJV)
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.That's it. That is the entire passage upon which denial of birth control is based. (and masturbation as well)
So what is happening in this scene? Honestly, it's a pretty wild story, especially by today's standards. Onan is King Judah's son. Er, the eldest, was struck down by God for being horribly wicked. That's why it says "slew him also." The Lord didn't have a lot of patience with Judah's boys; He had important business and they weren't right for it.
Onan, as Judah's second son, was to take Er's wife Tamar as his own to provide Er with heirs, and he does, but Onan doesn't want his kids to be considered Er's. As Er's rival he wouldn't have children of his own, and perhaps he wanted his own tribe to propagate. At any rate, Onan was apparently denying the Jewish people their next king by doing this.
Ultimately, Judah himself sleeps with Tamar because he mistakes her for a prostitute--she tricks him because she wasn't given the third son Shelah to marry as was her due--and she has twin boys. Tamar is actually a very strong figure here, as she demands what she believes is her right: to be the mother of the tribe. She demands Onan after Er dies, and when she does not receive the third son she risks her life by taking matters into her own hands. (It's also worth noting that God was fine with Judah sleeping with a prostitute, or at least with Judah thinking that he was. This is mentioned casually enough that it's hard to think it's the only time.)
So what does all this have to do with birth control?
There is literally nothing in these verses that says Tamar couldn't have told Onan she wanted to have sex but didn't want kids. There is also nothing that implies "spilling seed" would be a problem if he wasn't supposed to father the next king. We see from Tamar's later actions that she did want to have children and to be the mother of the future king, but that Onan just wasn't cooperating and was essentially using her.
So there is simply no reason that I can see why this passage is about God wanting women to have children every time they have sex.
The issue discussed in these verses is clear: God wanted an heir to
the king, and Onan didn't want to provide one. So God took him out.
These verses are about men doing what God commands, NOT about women having sex. Perhaps there is a story here about the need for men to respect women and their needs, or for womento forge their own destinies, but this is not about birth control or abortion at all.
Why am I not surprised that an all-male hierarchy would shift it around to justify their ideas for female behavior? I'm not surprised because the all-male hierarchy is in fact the root of the entire problem. Men get stuck on the minor issue of sex and their own desires, instead of on the incredibly huge deal of the creation of the Kingdom of Judah, and the bringing together of the tribes.
Why are Onan and Er even important then? There's a lot of disagreement on that, but some scholars say the two men are an etiological representation, intended to establish the relation of two other extinct tribes to Judah. That makes some sense, especially in regard to Onan not wanting to provide Er with heirs, and the fact that they are both bypassed, and killed by God. It's an interesting theory at least.
There is a bit more in the Bible that gets called out on occasion to oppose birth control (and abortion), namely that children are referred to as a "gift from God" --which they truly are--and that to deny God's gift is to oppose Him. But it's worth noting that the Bible also calls a wife a "gift from God" --which mine truly is, others may not be so lucky--yet there is no church requirement against resisting marriage. In fact we have just the opposite with celibate priests.
So that's how I read it. What's your opinion?