Musnad Ahmad 8:119

Yahya ibn Sa'id narrated to us, from 'Umar ibn Nabih, Abu 'Abdullah al-Qaraz narrated to me, he said: I heard Sa'd ibn Malik saying: I heard the Messenger of Allah, peace and blessings of Allah be upon him, saying: "Whoever intends evil for the people of Medina—or intends harm for them—Allah will dissolve him just as salt dissolves in water."