I like Mrs. Don-o’s answer. Is this Catholic, Christian, or stock-Christian? (entertaining thought/temptation in the mind being a sin...)
It is plucked straight out of Jewish law, not surprisingly. It’s actually one of my pet peeves against Dennis Prager, who I heard speak once of thinking about sin being not a sin (or a lesser sin.) When Judaism demands control of the actiona, speech, and even the thoughts (after they’ve “popped” into conscious thought.)
Interestingly, we believe the very WILL, which channels the unwanted thoughts, can be changed... which is why I believe the very (supposed) nature of homosexuality can be changed.
I can't speak for non-Catholic Christians, but I do know that the very definition of sin in Catholicism involves the will. Things that are unwilled cannot, by definition, be imputed to you as personal sin. Therefore things that you dream, or unbidden thoughts suggesting sin but which you struggle against, or something done by a mentally incapacitated person, cannot be sins, though they be contrary to the Moral Law. On the other hand, even willfully entertaining the thought of illicit sex, or revenge, or murder, or humiliating somebody else, is a sin, because it is cooperation with the corruption of the will. Pleasurably thinking of it is a sin; actually planning it is even a worse sin, even if you don't actually carry it out. Intentionally fantasizing or planning are considered interior acts.
Jesus speaks of these things in the Sermon on the Mount. I hadn't realized that that was also in the Hebrew Scriptures, but that's great. I'm interested. Can you give me a chapter and verse?
Delighted when Jesus turns out to be (no surprise!) a good Jew.