I have prayed behind a qadiyani twice without knowing that it was prohibited. Do i have to repeat my salat or not?
Al-jawab billahi at-taufeeq (the answer with Allah's guidance)
There is scholarly consensus (Ijma`) that Qadiyanis or Ahmadiis are not Muslims. So it is therefore impermissible to pray behind a Qadiyani. However, if one had prayed behind a Qadiyani knowing or not knowing will have to repeat the Salah.