[Explanation]
The author—may Allah have mercy on him—relates from Saʿid ibn Zayd (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said, “The truffle is part of the manna, and its water is a cure for the eye.”

The truffle is what people commonly call al-fujaʿ (the desert truffle). It sprouts in abundance after heavy rainfall, especially during the seasonal rains. Well known for its pleasant taste, it grows on the earth’s surface, and once it has matured people pick it without expense or toil. For that reason the Prophet (peace be upon him) described it as “part of the manna,” meaning a favor that Allah has granted His servants with ease and without hardship.

His words “its water is a cure for the eye” mean that the liquid extracted from it—when an eye ailment is caused by excessive moisture—serves, by Allah’s permission, as a remedy, for the truffle’s fluid, though liquid, possesses a drying quality: it dries the eye and removes the excess moisture. Thus “its water is a cure for the eye” is not to be understood of every eye disease, but specifically those whose cause is moisture; such conditions are healed, if Allah wills.

How is this water obtained? It is said that the truffle is first heated over a fire until it softens and is then pressed, and it is said that it is cut into small pieces and squeezed vigorously, whereupon a small amount of liquid emerges.

Allah is the One who grants success.