I actually did learn this one in sunday school, believe it or not. The widow needed a man and some kids to guarantee she'd be taken care of later in wife. By pulling out, he was basically manipulating her into sex and then trying to skip out on the whole being a father and taking care of her and any kids part. So god smote his ass.
God is apparently not a fan of deadbeats and my guess is neither were the Israelites who murdered this literal fucker and claimed it was Jehovah.
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