1. It is a positive commandment, based on the words of the prophets, to
fast on certain days of the year when calamities occurred to our ancestors.
The purpose of these fasts is to arouse our hearts and motivate us [to
pursue] the paths of repentance. It should serve as a reminder of our
misconduct ("ma'aseinu ha'ra'im"), and that of our ancestors, which
resembles our own, and which ended up causing these calamities to occur to
them and to us. The recollection of these matters should inspire us to
repent and improve our behavior, as [Leviticus 26:40] states: "They shall
confess their sin and the sin of their fathers."
Therefore, on these days, a person is obligated to examine his behavior and
repent for [any misconduct]. [This, and] not the fasting per se, is the
fundamental objective. Thus, in regard to the people of Nineveh, [Jonah
3:10] states: "And G-d saw their deeds..." [The Talmud in tractate Ta'anis
16a] relates: The prophet does not say: "And G-d saw their sackcloth and
fasting," but rather, "And G-d saw their deeds, that they had turned from
their evil ways."
Fasting is only a preparatory step for repentance. Therefore, those people
who fast, but go on pleasure strolls and waste the entire day with useless
activities, have fulfilled the secondary aspect [of the day,] while
ignoring its primary intent.