الكمأة من المن وماؤها شفاء للعين

Your Guide to English

 وعن سعيد بن زيد رضي الله عنه قال سمعت رسول الله صلى الله عليه و سلم يقول : [ الكمأة من المن وماؤها شفاء للعين ] متفق عليه

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

Commentary:

Al-Manna is the famous kind of food which Allah bestowed upon Banu Israel. As-Salwa was a kind of bird resembling the quail. It was slaughtered and then eaten. Al-Manna was a sweet substance which appeared on the trees or stones. It was sweet like honey and after drying, it took the form of gum. According to others, it was honey or sweet water (Tafsir Ahsan-ul-Bayan). The truffle is similar to Al-Manna. This means that as Banu Israel were given food without toil, so we find truffle in nature without effort. The juice of truffle is useful in curing some diseases of the eye. This prescription was suggested by the Prophet (PBUH). It is surely beneficial.

رياض الصالحين بالعربية والإنجليزية - (ج 1 / ص 2436)
 Iml?? m? manna bihi al-Ra?m?n min wuj?h al-i?r?b wa-al-qar???t f? jam?? al-Qur??n (Arabic Edition)
HIDDEN MANNA FOR THE END TIMES