Sahih Muslim
The Book of Pilgrimage (Kitab Al-Hajj)
Book Number: 007 / Hadith Number: 3194
Abu Huraira (Allah be pleased with him) reported that Abu'I-Qasim (Mubammad, 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.