عن أنس بن مالك رضي الله عنه عن النبي ﷺ قال: «كفارة من اغْتَبْتَهُ أَنْ تستغفر له».
Anas ibn Mālik (may Allah be pleased with him) reported that the Prophet (may Allah's peace and blessings be upon him) said: "The expiation of backbiting a person is to ask forgiveness for him."
Whoever commits the major sin of backbiting his Muslim brother and he wishes to be absolved, then the expiation of that is to ask Allah's forgiveness for the person he backbit.