[dianakroshXX]

Such claims require proof.

What I have read, very briefly, and may or may not be accurate, is that some Hanafis, in the Medieval period, said that one could not marry a Shafi'i. This might have been due to a bit of fanaticism, but its reasoning was grounded in something concrete.

Hanafis, who mostly follow Maturidi aqeedah, believe that eman remains constant: Either you believe in Allah, the books He sent, etc. or you don't. What increases and decreases is the quality of faith, yaqeen in this belief, etc. Asharis, on the other hand, mostly Shafii's in question, believe that eman itself can increase and decrease in and of itself. Thus, when asked if one is a believer, a Hanafi following Maturidi aqeedah would say, "Yes, I am a believer." On the other hand, a common Shafi'i answer to such a question would be, "I am a believer, inshaAllah." Certain Hanafis said that through Shafi'is saying "InshaAllah," in response to a question about being a believer, they vocalized that they were unsure of their belief, thus negating their eman, and since they vocalized it, their Islam, thus making it impossible to apply Islamic laws to them in this life, and subsequently making it impossible for a Muslim to wed them.

Also, the sahaba and tabi'een differed in the ways they prayed. Not praying behind someone else due to fiqh differences had no basis amongst them.