Sahih Muslim Book 7, Hadith Number 3194.

Chapter : Allah will punish those who intend to do any harm to the citizens of Medina.

Abu Huraira (Allah be pleased with him) reported that Abu’I-Qasim (Muhammad, may peace be upon him) said: He who intends to do harm to the people of this city (that is, Medina). Allah would efface him as salt is dissolved in water.