I heard the Prophet ﷺ say, "Truffles are part of the manna, and their juice is a cure for the eye."
سمعت النبي ﷺ يقول: الكمأة من المن وماؤها شفاء للعين.
Bukhari narrated it in the Book of Medicine (5708), and Muslim in the Book of Drinks (2049: 158), both from Muhammad bin Muthanna, who said, Ghundar told us, Shubah told us, from Abdul-Malik, I heard Amr bin Hurayth say, I heard Saeed bin Zayd, and he related it. Abu Awana narrated it in his Musnad (8347, 8349) from Abbas bin Muhammad Duri, from Yazid bin Harun, from Shubah with the same chain, adding to it, "And ajwa dates are from Paradise," and his saying "truffles," these grow in the ground without being planted.His saying "from manna" compares truffles to the manna that Allah sent down upon Banu Israil without any toil or effort, without planting or watering.His saying "its water is a cure for the eye" means that its liquid is pressed out and dripped into the eyes. Other remedies, such as kohl, may be mixed with it, and it is then used as eyeliner. This is something known through experience.