Musnad Ahmad 30:1188

Rawh narrated to us, Sa'id narrated to us, from Qatadah, from Shahr ibn Hawshab, from 'Abd al-Rahman ibn Ghanam, from Abu Hurayrah, that the Messenger of Allah (peace and blessings of Allah be upon him) went out to them while they were mentioning truffles, and some of them were saying: "The smallpox of the earth." The Prophet (peace and blessings of Allah be upon him) said: "Truffles are of the Manna, and their water is a cure for the eye. And the Ajwa date is from Paradise, and it is a cure for poison."