Asma bint Yazid (may Allah be pleased with her) narrates that the Messenger of Allah (peace and blessings be upon him) said: "Whoever does not allow his (Muslim) brother to be backbitten in his absence, it is a right upon Allah to free him from the fire of Hell." Its chain is Hasan. Narrated by Al-Bayhaqi in Shu'ab al-Iman.