Musnad Ahmad 30:3508

Abu Dawud narrated to us, Hisham narrated to us, from Qatadah, from Shahr ibn Hawshab, from Abu Hurairah, that the Prophet, peace and blessings of Allah be upon him, went out to his companions while they were mentioning truffles. They said: "Do you consider them the smallpox of the earth?" The Messenger of Allah, peace and blessings of Allah be upon him, said: "Truffles are of the manna, and their water is a cure for the eye. And the Ajwa date is from Paradise, and it is a cure for poison."