The Messenger of Allah ﷺ said, "Truffles are part of the manna which Allah sent down upon the Children of Israil, and their juice is a cure for the eye."
قال رسول الله ﷺ: الكمأة من المن الذي أنزل الله على بني إسرائيل، وماؤها شفاء للعين.
Bukhari narrated it in the tafsir (4478), and Muslim in the drinks (2049: 160), both from the hadith of Sufyan, from Abdul-Malik bin Umayr, who said, I heard Amr bin Hurayth say, I heard Saeed bin Zayd say, and then he related it. The wording given here is Muslim's.Mujahid said, Manna is a kind of resin, and salwa is a bird. There are other hadiths on this subject mentioned in the book on medicine.