Abdur Rahman bin Nawfal Al-Ashja'i (may Allah have mercy on him) narrates from his father that a man said: O Messenger of Allah (peace be upon him)! I have newly embraced Islam, tell me of a deed that will completely purify me from shirk. The Prophet (peace be upon him) said: Recite Surah «قُلْ يَا أَيُّهَا الْكَافِرُونَ» . The narrator says that from that day until his death, there was not a single day or night when his father did not recite this Surah.