Musnad Ahmad 941:69

Muhammad ibn Bishr narrated to us, Muhammad ibn ‘Amr and Yazid narrated to us, they said: Muhammad ibn ‘Amr informed us, from Muhammad ibn al-Munkadir, from ‘Amir ibn Sa‘d ibn Abi Waqqas, from Usamah ibn Zayd, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "If you hear of the plague in a land, do not enter it, and if it occurs while you are in a land, do not leave it, fleeing from it."