cellio | daf bit: Nedarim 41

Rabbi Alexandri said in the name of Rabbi Hiyya ben Abba: A sick man does not recover from his sickness until all his sins are forgiven him, as it is written, Who forgiveth all thine iniquities; who healeth all thy diseases (Ps. 103:3). Rabbi Chamnuna said: He then returns to the days of his youth, for it is written, His flesh shall be fresher than a child's: he shall return to the days of his youth (Job 33:25). (41a)

(Note that Rabbi Alexandri says nothing here about the implications of a man not recovering. It does not follow that failure to recover means one has not been forgiven; he leaves the option completely open. That's much kinder than the view that suffering is necessarily punishment for sin. It also serves as a call to action for the sick person.)