Musnad Ahmad 31:463

Asbat ibn Muhammad narrated to us, al-A’mash narrated to us, Ja’far ibn Iyas narrated to us, from Shahr ibn Hawshab, from Jabir ibn Abdullah and Abu Sa’id al-Khudri, they both said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The truffle is of the manna, and its water is a cure for the eye. And the Ajwa is from Paradise, and it is a cure for poison."