Al-Kalbi said concerning this verse: "Indeed, those who accuse chaste, unaware, believing women are cursed" [Surah al-Nur: 23]: What is meant by this verse is specifically the wives of the Prophet (peace and blessings be upon him). As for one who accuses an ordinary woman among the Muslims, he is a sinner (fasiq), as Allah has said, or else he repents.
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 19537