Muwatta Imam Malik (Riwayat Ibn al-Qasim)

It is narrated from Abdullah bin Amir bin Rabee'ah Al-Adawi (may Allah be pleased with him) that Sayyiduna Umar bin Al-Khattab (may Allah be pleased with him) set out towards Syria (for jihad). When he reached Sargh (a place near Syria, in the valley of Tabuk), he learned that an epidemic (plague) had spread in Syria. Then Sayyiduna Abdur Rahman bin Awf (may Allah be pleased with him) informed him that the Messenger of Allah (peace and blessings be upon him) said: "When you hear of its (the epidemic's) occurrence in any land, do not go there, and if it spreads in the land where you are present, do not flee from it in escape." So Umar bin Al-Khattab (may Allah be pleased with him) returned from Sargh.