As for what is recommended, some of them are restricted to the desired time, such as fasting the white days, Mondays, Thursdays, and similar days and months, and some are restricted to the situation, such as fasting one day and breaking the fast on another day, which is the most just of fasts, and such as fasting for the sake of God, and some are not restricted to a time, which is for a person to fast whenever he wants, voluntarily doing so.