[@Dinh AaronMk] Ok, I never meant to be start a debate, just giving a friendly suggestion that something like that wasn't the norm, and as Vlagei said, some things happen even if out of the norm or taboo. 
I think, as it is such a minor issue, I'll leave it at that :) 

Edit: Ninja'd xD
I was thinking more of a tribe loyal to the Caliph that goes about doing his bidding or giving soldiers to the cause etc.