Yahya related to me from Malik from Muhammad ibn al-Munkadir andfrom Salim ibn Abi'n-Nadr, the mawla of Umar ibn Ubaydullah that Amiribn Sad ibn Abi Waqqas heard his father ask Usama ibn Zayd, "Have youheard anything from the Messenger of Allah, may Allah bless him andgrant him peace, about the plague?" Usama said, "The Messenger ofAllah, may Allah bless him and grant him peace, said, 'The plague is apunishment that was sent down on a party of the Banu Israil or whoeverwas before them. When you hear of it in a land, do not enter it. If itcomes upon a land and you are in it, do not depart in flight from it.'"Malik said that Abu'n-Nadr said, "That is, do not departwith no other intention but flight."
USC-MSA web (English) reference: Book 45, Hadith 23
Arabic reference: Book 45, Hadith 1622