Sahih Bukhari | Volume 8 | Hadith Number 59A

Narrated by 'Aisha
A man asked permission to enter upon the Prophet. When the Prophet saw him, he said, "What an evil brother of his tribe! And what an evil son of his tribe!" When that man sat down, the Prophet behaved with him in a nice and polite manner and was completely at

ease with him. When that person had left, 'Aisha said (to the Prophet). "O Allah's Apostle! When you saw that man, you said so-and-so about him, then you showed him a kind and polite behaviour, and you enjoyed his company?" Allah's Apostle said, "O 'Aisha! Have you ever seen me speaking a bad and dirty language? (Remember that) the worst people in Allah's sight on the Day of Resurrection will be those whom the people leave (undisturbed) to be away from their evil (deeds)."