Sometimes a person is afflicted with illness to inspire him to repent. The merit he has accrued during his life protects him during his illness. If a sick person recovers from his illness and is cured, it is a clear sign that his sins have been forgiven.

Rav Yitzhak son of Rav Yehuda said: A person should always pray that he will not become ill, for if he becomes ill they say to him in Heaven: First bring proof of your merit, then be rid of your illness.

Rabbi Alexandri said that Rabbi Hiyya bar Abba said: A sick person recovers from his illness only when God forgives him for all his sins, as it is stated: “It is He who forgives all your sins, who heals all your diseases” (Psalms 103:3).

“You change his bedding during his illness” (Psalms 41:4). Rav Yosef said: This is to say that illness causes his studies to be forgotten.

Rabbi Levi said: As the parable says: A gate that is not open for mitzvot will ultimately be open for the doctor.

“For I am lovesick” (Song of Songs 2:5). The congregation of Israel said before the Holy One, blessed be He: Master of the Universe, all the illnesses that You bring upon me are in order to cause me to love You. (Shabbat 31b; Nedarim 41a; Shir HaShirim Rabba 6; Shir HaShirim Rabba 2)