Is backbiting repelled by saying, "Astaghfirullah, do not backbite," and does the one who says it fall under the virtue of protecting the flesh from the Fire with an angel, or is it conditioned upon saying, "You are mistaken, we have known nothing but good from him," which might anger a friend?

Many texts have been narrated regarding the virtue of defending a Muslim's honor and sanctity in their absence. Among them is what Anas narrated from the Prophet, peace be upon him: "Whoever has his Muslim brother backbitten in his presence – and he is able to help him – if he helps him, Allah will help him in this world and the Hereafter. And if he does not help him – and he is able to help him – Allah will seize him for it in this world and the Hereafter." And from Asma bint Yazid: "Whoever defends his brother's flesh from backbiting, it is a right upon Allah to free him from the Hellfire." And from Abu Darda: "There is no Muslim who defends the honor of his brother except that it is a right upon Allah to defend him from the Hellfire on the Day of Resurrection." And from Jabir: "There is no Muslim man who abandons a Muslim man in a place where his sanctity is violated and his honor is diminished except that Allah will abandon him in a place where he loves His help. And there is no Muslim man who helps a Muslim in a place where his honor is diminished and his sanctity is violated except that Allah will help him in a place where he loves His help."

Also, Abu Dawud narrated from Sahl bin Mu'adh, from his father, from the Prophet, peace be upon him: "Whoever protects a believer from a hypocrite – he (the narrator) said, 'I think he said' – Allah will send an angel to protect his flesh on the Day of Resurrection from the Hellfire. And whoever accuses a Muslim of something intending to disgrace him, Allah will detain him on the bridge of Hell until he retracts what he said." There is no specific wording required for defense; rather, anything that defends the Muslim and deters the aggressor is sufficient. Merely forbidding the backbiter and saying to him: "This is not permissible for you," is sufficient. And if he says something similar to what Mu'adh ibn Jabal said to one who backbit Ka'b ibn Malik: "What a terrible thing you have said! By Allah, we know nothing but good about him," that is good.