Sayyiduna Jubayr bin Mut'im (may Allah be pleased with him) narrates: The Messenger of Allah (peace and blessings be upon him) said: "Indeed, Allah, the Mighty and Majestic, tests His servant with illness until He expiates every sin from him."
Hadith Referenceالمعجم الكبير للطبراني / باب الجيم / 1535