(48) باب مَا يَجُوزُ مِنِ اغْتِيَابِ أَهْلِ الْفَسَادِ وَالرِّيَبِ
Narrated `Aisha:
A man asked permission to enter upon Allah's Messenger (ﷺ). The Prophet (ﷺ) said, "Admit him. What an evil brother of his people or a son of his people." But when the man entered, the Prophet (ﷺ) spoke to him in a very polite manner. (And when that person left) I said, "O Allah's Messenger (ﷺ)! You had said what you had said, yet you spoke to him in a very polite manner?" The Prophet (ﷺ) said, "O `Aisha! The worst people are those whom the people desert or leave in order to save themselves from their dirty language or from their transgression."
Reference: Sahih al-Bukhari 6054
In-book reference: Book 78, Hadith 84
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 8, Book 73, Hadith 80