Anas bin Malik (may Allah be pleased with him) narrates: When the head of Husayn bin Ali was brought to Ubaydullah bin Ziyad, he began poking at its teeth with a stick in his hand, saying: How beautiful his teeth were! So I said: By Allah, I will certainly tell you something that will displease you: I saw the Messenger of Allah (peace and blessings be upon him) kissing the very place of that mouth where your stick is striking.
Hadith Referenceالمعجم الكبير للطبراني / باب الحاء / 2865