.I speak not of such a fast as most persons keep, but of real fasting; not merely abstinence from meats, but from sins as well. For the nature of a fast is such that it does not suffice to deliver those who practice it unless it is done according to a suitable law. So that when we have gone through the labor of fasting we do not lose the crown of fasting, we must understand how and in what manner it is necessary to conduct the business since the Pharisee also fasted, but afterward went away empty and destitute of the fruit of fasting. The Publican did not fast, and yet he was accepted in preference to him who had fasted in order that you may learn that fasting is unprofitable unless all other duties accompany it.
Fasting is a medicine. But like all medicines, though it be very profitable to the person who knows how to use it, it frequently becomes useless (and even harmful) in the hands of him who is unskillful in its use.
I have said these things not that we may disparage fasting, but that we may honor fasting. For the honor of fasting consists not in abstinence from food, but in withdrawing from sinful practices, since he who limits his fasting only to abstinence from meats is one who especially disparages fasting.