Musnad Ahmad 10:23

Hajjaj and Yazid—the meaning being the same—said: Ibn Abi Dhi’b informed us, from al-Zuhri, from Salim, from ‘Abdullah ibn ‘Amir ibn Rabi’ah, that ‘Abd al-Rahman ibn ‘Awf informed ‘Umar ibn al-Khattab, while he was traveling on the road to Syria, regarding the Prophet (may Allah bless him and grant him peace), who said: "Indeed, this plague was a punishment with which the nations before you were tormented. So, if you hear of it in a land, do not enter it because of it. And if it occurs in a land while you are in it, do not exit it, fleeing from it." He said: So ‘Umar ibn al-Khattab returned from Syria.