Musnad Ahmad 5:20

Narrated to us Abdullah, narrated to me Abu Ibrahim al-Turjumani, narrated to us al-Faraj ibn Fudalah, from Muhammad ibn Abdullah ibn Amr ibn Uthman, from his mother Fatimah bint Husayn, from Husayn, from his father, from the Prophet, peace be upon him, who said: "Do not persist in looking at those afflicted with leprosy. And if you speak to them, let there be between you and them the distance of a spear's length."