Musnad Ahmad 30:1254

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 Hurairah 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, just as Ibrahim asked You for the people of Makkah, and the like thereof with it." "Indeed, Medina is interlaced with angels; upon every mountain pass of it are two angels guarding it. The plague shall not enter it, nor the Dajjal. Whoever intends it with evil, Allah will dissolve him just as salt dissolves in water."