Doing some search in Arabic, I found this practice mostly mentioned in Arab Christian websites. Also found mentions to it by bizarred Muslims basically saying wtf is this!?

The verse in the Quran that is used to prove this practice is (Quran 23:1-9). And obviously it doesn't.

I searched for a hadeeth (saying of the prophet) regarding that, but didn't find any.

I searched the fatwa (the teachings of modern day scholars) and found 3 mentions. One says that it's forbidden to do it out of marriage. And the other two say that if you & your wife are into that, you can do whatever you want while still having the same rules as sex (no sex during fasting, during pilgrimage, etc).