The most severely tested of people are the Prophets, then those who follow them

It is narrated from Sayyidah Fatimah (may Allah be pleased with her) that she said: I went along with some women to visit the Messenger of Allah (peace and blessings be upon him) in his illness, and I saw that a waterskin (siqa', a leather bag) of water was hung above him, its water dripping onto him because of the intensity of the fever's heat. I said: "O Messenger of Allah! If you were to supplicate to Allah, He would remove this affliction from you." So he (peace and blessings be upon him) said: "Indeed, the people most severely tested are the Prophets, then those who are closest to them (in rank)."

It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "Hold fast to cow's milk and its ghee, and beware of its meat, for its milk and ghee are medicine and cure, whereas its meat is disease."
This hadith has a sahih (authentic) chain of narration, but the two Shaykhs (Bukhari and Muslim) did not record it.