It is narrated from Sayyiduna ‘Ubada bin Samit (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) took a pledge from us on six matters, just as he took from the women: “Not to associate anything with Allah, not to steal, not to commit adultery, not to kill your children, not to accuse one another falsely, and not to disobey me in any good that I command.” So whoever commits any of these mentioned crimes and is punished for it in this world, that will be an expiation for his crime. And whoever’s punishment is deferred, his matter is with Allah Almighty; if He wills, He will punish him, and if He wills, He will forgive him. Imam Shafi‘i (may Allah have mercy on him) said: Whoever says something about a man that is not in him, he has slandered him. (In one version: Whoever lies about his brother, he has bitten him with his teeth / backbiting / slander — all these meanings are included in it.)
Hadith Referenceالسنن المأثورة / باب الجهاد / 626
Hadith Takhrijسنن ابن ماجہ الحدود، باب الحد کفارہ، رقم: 2603 وقال الالبانی صحیح، مسند احمد: 341/37، رقم: 22669 وقال الارنوؤط اسنادہ صحیح علی شرط مسلم۔