I was not talking about what is written on this flag (I already knew what was on it, and that shahada was already used for some flags and on some clothes during medieval area), but about these two flags... with exact same colors, size, proportions.
This flag is used by Al-Nosra, the Shebabs, Al-Qaeda and many more, it is a fact.
These movements are killing unarmed people, children, people from other faith.
Ok now, if there are proofs that this flag, with exact proportions, size, colours and police was already used by abbasid caliphate (and I don't speak only about shahada), I would appreciate if you could post the sources (medieval muslim pictures, or historian research etc...)
I will censoring myself and not post here all the different propaganda videos made by these movements where they are proud to kill children and unarmed people who are even not fighting against them. You can find them really easily on youtube.