Sahih al-Bukhari 4639
صحيح البخاري#4639SahihNarrated Sa`id Ibn Zaid:The Prophet (ﷺ) said, "Al-Kam'a is like the Manna (sweet resin or gum) (in that it grows naturally without human care) and its water is a cure for the eye diseases
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih al-Bukhari is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 65:161