Musnad Abu Ya'la al-Mawsili 160:12

Shayban narrated to us, Uqbah—meaning al-Asamm al-Rifa'i—narrated to us, from Shahr ibn Hawshab, who said: Abu Hurairah narrated to me that the companions of the Messenger of Allah (may Allah bless him and grant him peace) disputed regarding the truffle. Some of them said, "I see it as the tree which was uprooted from above the earth, having no stability," while others refrained from speaking about it. That reached the Messenger of Allah (may Allah bless him and grant him peace), so the Prophet (may Allah bless him and grant him peace) said: "The truffle is indeed from the manna, and its water is a cure for the eye. And the Ajwa date is from Paradise, and it is a cure for poison."