Musnad Abu Ya'la al-Mawsili 6:3

Abu Musa narrated to us, Mu'adh bin Hisham narrated to us, my father narrated to us, from Qatadah, from 'Ikrimah bin Khalid, from Ibn Sa'd, from his father, from the Prophet (peace and blessings of Allah be upon him), who said: "If the plague is in a land, do not enter it. And if it occurs in a land while you are in it, do not depart from it."