Musar for Chagigah 44:6

At this point I would like to add my own comments while maintaining the utmost respect for the views expressed by the Tosafists I have quoted. Their answers seem rather forced in this matter. I am convinced that Samuel also admits that a person who has committed some wrong needs to flagellate himself and may certainly impose fasting upon himself as a means of self-flagellation. He may continue to do so until he is sure that such self-flagellation has removed the taint of sin from him. We have King David on record as saying: "my knees have given way from fasting" (Psalms 109,24). The Talmud is on record that the teeth of Rabbi Joshua had become blackened due to too much fasting. Here the author proceeds to list numerous similar examples of great scholars who had imposed fasting as well as other means of self-flagellation upon themselves. The author feels that it is clear that what Samuel had said applied only to people who are certain that they have not committed any sin. Such a person would be remiss if he subjected himself to fasts voluntarily. When Samuel said that a person may inflict injury upon himself [through fasting] he obviously referred to the kind of person who used this to atone for sin. In such a case it is not only permitted, but is a מצוה. If Samuel nonetheless uses the expression that it is "permissible," this is only since the Talmud wanted to contrast the expression with the case of other persons who are "forbidden" to impose such flagellation upon him.