I took a few classes on Islamic history in college and some of the similarities between the practices of early Sufis (wearing hair shirts, repetitive/constant prayers, etc.) reminded me a lot of what I had heard about early Eastern (pre-schism) Christian monks, specifically those collectively referred to as the "Desert Fathers". This leads me to believe that there was probably a sharing of ideas between these two mystical societies. I tried looking for research about this on JSTOR but I so far haven't been able to find anything.
Do any of you know anything about this subject? I want to do research in this field (if it actually is a real field).
I was a religious studies minor in college and, my professors did mention that there is possible evidence that Muhammad knew about Christian traditions and methods, since he grew up around merchants, whom would spread their knowledge and understandings of their findings of the world quite often.
I've noticed similar things, and this is what I often tend to come back to.