My favorite part is that if you actually read this story it's not even about masturbation, it's about how shitty it is to try and rules-lawyer your way out of doing the right thing.

Onan's brother died and left a childless widow. In Jewish culture at that time, as a widow, she would've needed a son to collect the inheritance / be taken care of, etc. The workaround (in lieu of not being misogynists given that these were ye olden times) was that your brother in law would knock you up and that kid would legally count as your dead husband's for the purposes of inheritance.

But Onan thinks he's reeeaaaal clever and figures if she just magically can't get pregnant, he could just keep all that land, tents, horses, and whatever else. So he just keeps pulling out, she never gets pregnant and figures he's home free and puts his brother's widow out on the street to become a prostitute. There's some specific symbolic way that he gets his divine comeuppance for all this but I can never remember that part.

This was just the example my childhood pastor used to like using when he explained the problems with just letting someone else tell you what the Bible means instead of reading it for yourself. The man was very educated and gave a lot of sermons on the historical cultural context of a lot of the texts. In fact I'm pretty sure all of my childhood pastors had Master's degrees.

This is also the same guy that founded the interfaith community in my city to promote cultural exchange and coordinated charity efforts. Basically Fred Rogers' spiritual twin was my childhood pastor; if they weren't alive at the same time it would have me believing in reincarnation (they even looked similar and were even both Presbyterian).

The man had a congregation in the hundreds and he knew the name of every person in every family, what their jobs were, what their kids were studying in college, and if they had any sick relatives, and would stand by the gate at the end of every service shaking every single persons hand and chatting about that stuff for a minute or two each. When my brother died he was on our doorstep within an hour of the cops notifying us. Regardless of how my personal spiritual beliefs have waxed or waned at various points it took me a looong time to understand how someone in that position could hurt people through either malice or incompetence.