Is it permissible to backbite a person who does not pray, knowing that one who does not pray may be an infidel?

Backbiting is forbidden by Islamic law, as evidenced by the Quran, Sunnah, and scholarly consensus; it is considered one of the grave sins. No exceptions are made unless there is an overriding benefit, such as advising someone who intends to marry a person who does not pray, with the intention of giving sincere advice and not out of personal whims. Sheikh al-Islam stated that the saying "there is no backbiting against a profligate" is not a prophetic hadith, but rather a saying of Al-Hasan al-Basri, intended to warn people against such an individual. He clarified that revealing the faults of a profligate person must be done for the purpose of sincere advice and seeking Allah's pleasure, not out of personal whim or worldly animosity.