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also you are wrong in travhee, prophet pbuh did not discourage such act he pbuh told i am affraid that such salah will frad on you, so, simply what ahlul sunna said that this is sunnat-e-moqida (if you perform you will get revard if not you will not get reward this is not necessary).
and lastly you wrong again, first you have to prove that ist to khalifa ra did anything against sunnat of our prophet pbuh then blame some one. hz. usman ra was much better than hz. ali ra at that era since hz. usman ra was also son of low of prophet pbuh he ra husband of two doughter of prophet pbuh, and he ra is in also ashra-e-mubashra.