Sahih Muslim Book 26, Hadith Number 5494.

Chapter : Plague, ill omen and magic.

Usama b. Zaid reported that Allah’s Messenger (may peace be upon him) had said: Plague is the sign of a calamity with which Allah, the Exalted and Glorious, affects people from His servants. So when you hear about it, don’t enter there (where it has broken out), and when it has broken out in a land and you are there, then don’t run away from it.