Musnad Abu Ya'la al-Mawsili 6:116

Zuhayr narrated to us, Uthman ibn Umar narrated to us, Usamah ibn Zayd narrated to us, Abu Abdullah al-Quraz narrated to us that he heard Sa’d ibn Malik and Abu Hurayrah saying: The Messenger of Allah (peace and blessings of Allah be upon him) said: "O Allah, bless the people of Medina in their Medina, and bless them in their sa’ (measure), and bless them in their mudd (measure). O Allah, indeed Ibrahim is Your servant and Your close friend (khalil), and I am Your servant and Your messenger. And indeed, Ibrahim asked You for the people of Makkah, and I ask You for the people of Medina the like of what Ibrahim asked You for the people of Makkah, and the like of it with it." "Indeed, Medina is surrounded by paths, upon every mountain pass of which are two angels guarding it. Neither the plague nor the Dajjal shall enter it. Whoever intends it with evil, Allah will dissolve him just as salt dissolves in water."