It's not and I wasn't even being serious. I was just trying to imagine what a spiritual tithe could possibly be, even though the idea seems kind of ridiculous.
However, if you were referring to Jacob vowing to give the tenth to God that is in Genesis 28:22. He never received the land, so his descendants who did receive it were required to fulfill his vow. That's not stated explicitly in scripture, but there it is and it's as good as any explanation for the existence of tithes.[/QUOTE]
I agree: it's not stated in Scripture. I leave it there and don't make more of it than that.