Musnad Ahmad 10:27

Ishaq ibn Isa narrated to us, Malik informed me, from al-Zuhri, from Abdullah ibn Amir ibn Rabiah, that Umar ibn al-Khattab set out for al-Sham. When he reached Sargh, news reached him that the plague had broken out in al-Sham. Abd al-Rahman ibn Awf informed him that the Messenger of Allah (peace and blessings of Allah be upon him) said: "If you hear of it in a land, do not advance toward it, and if it breaks out in a land while you are in it, do not depart from it fleeing from it." So, Umar ibn al-Khattab returned from Sargh.