From Sahih Bukhari (Hadith 6973):
Narrated `Abdullah bin 'Amir bin Rabi`a:`Umar bin Al-Khattab left for Sham, and when he reached a placed called Sargh, he came to know that there was an outbreak of an epidemic (of plague) in Sham. Then `AbdurRahman bin `Auf told him that Allah's Messenger (ﷺ) said, "If you hear the news of an outbreak of an epidemic (plague) in a certain place, do not enter that place: and if the epidemic falls in a place while you are present in it, do not leave that place to escape from the epidemic." So `Umar returned from Sargh
Reference: Bukhari 6973