Sahih al-Bukhari 4478
Sahih al-Bukhari · Book 65: Prophetic Commentary on the Qur'an (Tafseer of the Prophet (pbuh)) · "And We shaded with clouds and sent down on you Al-Manna and the quail,... (up to) wronged themselves." (V.2:57)
Narrated Sa`id bin Zaid:
حَدَّثَنَا أَبُو نُعَيْمٍ ، حَدَّثَنَا سُفْيَانُ ، عَنْ عَبْدِ الْمَلِكِ ، عَنْ عَمْرِو بْنِ حُرَيْثٍ ، عَنْ سَعِيدِ بْنِ زَيْدٍ ـ رضى الله عنه ـ قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " الْكَمْأَةُ مِنَ الْمَنِّ، وَمَاؤُهَا شِفَاءٌ لِلْعَيْنِ " .
Allah's Messenger (ﷺ) said, "The Kam'a (i.e. a kind of edible fungus) is like the Manna (in that it is obtained without effort) and its water is a (medicine) cure for eye trouble."