Is this Hadith sound?… It was narrated that the Prophet (peace be upon him) said: “Whoever says in Rajab ‘I ask Allah for forgiveness, there is no God but He alone, with no partner or associate, and I repent to Him’ one hundred times, and ends it with charity, Allah will decree for him mercy and forgiveness. And whoever says it four hundred times, Allah will decree for him the reward of one hundred martyrs.”

There is no basis for this hadith in the books of Sunnah and reports, and no narration is known for it with any of the scholars. Similarly, we could not find it in the books which deal with false and fabricated hadiths.