In the town of Liozna lived a Torah scholar who also responded to halachic (Jewish legal) questions. This Jew suffered from an incurable illness, and no medicine or remedy proved effective.
At that time, the Alter Rebbe, author of the Tanya, lived in Liozna and was known as "the Maggid of Liozna." The ill man came to him and requested a blessing for a complete recovery.
The Rebbe asked him how he ruled on a certain halachic question in the laws of treifot (disqualifying physical defects in animals). The man replied that he ruled it to be forbidden (treif). The Rebbe began to engage him in a halachic discussion, until the man was compelled to admit that, in truth, the case in question was kosher and not disqualified.
The Rebbe said to him: "Now you can be healed, because that was precisely your illness. As long as you believed that this illness was treif (incurable) – you could not be healed."
