The Prophet, on hearing a man reciting “Say, He is God, One” remarked, “It is certain.” I asked him what was certain, and he replied that it was paradise.
He reported the Prophet as saying, “If anyone who is about to sleep on his bed lies on his right side, then recites ‘Say, He is God, One’ a hundred times, the Lord will say to him on the day of resurrection, ‘My servant, enter paradise to your right’.”
Tirmidhī transmitted it, saying this is a hasan gharīb tradition.
Farwa b. Naufal quoted his father as saying that he had asked God's messenger to teach him something to say when he went to bed, and was told to recite, “Say, O infidels”, for it is a declaration of freedom from polytheism.
Anas reported the Prophet as saying, 'If anyone recites two hundred times daily, ‘Say, He is God, One’, the sins of fifty years will be wiped out, unless he is in debt.”
Tirmidhī and Dārimī transmitted it. The latter’s version has “fifty times”, and he did not mention “unless he is in debt.”