Musnad Ahmad 10:28

Ishaq ibn Isa narrated to us, Malik informed me, from al-Zuhri, from Abd al-Hamid ibn Abd al-Rahman ibn Zayd ibn al-Khattab, from Abdullah ibn Abdullah ibn al-Harith ibn Nawfal, from Abdullah ibn Abbas, that Umar ibn al-Khattab set out for al-Sham. When he reached Sargh, the commanders of the armies—Abu Ubaydah ibn al-Jarrah and his companions—met him and informed him that the plague had broken out in al-Sham—then he mentioned the hadith. He said: Then Abd al-Rahman ibn Awf came, and he had been absent for some of his needs, and said: "I have knowledge regarding this. I heard the Messenger of Allah, peace and blessings of Allah be upon him, say: 'If it is in a land and you are in it, do not leave it fleeing from it; and if you hear of it in a land, do not advance toward it.'" He said: So Umar praised Allah, then turned back.