Imam Bukhari apologized for smiling!
Once Imam Bukhari was in the masjid and waited for everyone to leave so that he could talk to Mash’ar (who was a blind man). Once everyone left, Imam Bukhari began crying and begged the man to forgive him.
The man was shocked and asked: “What for O’ Abu ‘Abdullah?” So Imam Bukhari answered: “Once as I was narrating Hadith to my students, you were dancing at a close distance and I smiled because of this and I fear that this may be backbiting that I have done against you.” The man replied: “Is that all, O’ Abu ‘Abdullah? Of course I forgive you!”
● [سير أعلام النبلاء | التاريخ والتراجم]
Imam Bukhari 