Shabab al-Usfuri narrated: It was in the year 6 AH; the expedition of Banu al-Mustaliq took place, and on that expedition the people of the slander (ifk) said what they said about Sayyidah Aishah, and the Qur'an was revealed in that connection: "Indeed, those who brought forth the slander", the verses.
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 19565