Sa'id bin Zaid (May Allah be pleased with him) reported:
I heard the Messenger of Allah ﷺ saying, "Truffle (edible fungus) is a species of Al-Manna and their water cures eye diseases."

[Al-Bukhari and Muslim].

وعن سعيد بن زيد رضي الله عنه قال: سمعت رسول الله ﷺ يقول: "الكمأة من المن، وماؤها شفاء للعين" ((متفق عليه)).