Musnad Ahmad 30:884

Muhammad ibn Ja'far narrated to us, Shu'bah narrated to us, from Abu Bishr, from Shahr ibn Hawshab, from Abu Hurairah, from the Prophet, may Allah bless him and grant him peace, who said: "The truffle is of the Manna, and its water is a cure for the eye. And the Ajwa is from Paradise, and its water is a cure for poison."