After prayer, fasting is the second ascetic practice you should begin as part of an Orthodox way of life. Of course, if you do not have sufficient faith to participate in the regular worship services, to participate regularly in the sacraments, or time for daily prayer, fasting will not be of much help to you. Fasting is a practice that was shown to us by Jesus as well as the prophets of the Old Testament. Jesus fasted for 40 days at the start of His public ministry. We are told “he ate nothing.” The Prophet David fasted, “I ate no delicacies, no meat or wine, no did I anoint myself.“ (Daniel 10:3) Ester instructed Mordicai, “ Go, gather all the jews... and hold a fast on my behalf and neither eat nor drink for three days, night and day. I and my maids will also fast as you do.” (Ester 4:16) Paul engaged in a three day absolute fast following the encounter with the living Christ (Acts 9:9). Moses and Elijah fasted for forty days. (Deut 9:9, 1Kings 19:8)
Jesus also asked us to fast. He said that we can overcome the devil only through “prayer and fasting”. (Matt 17:21) In Matt 6:16 Jesus says “When you fast.…” He did not say "If you fast." He assumes that you will fast and gives instruction on how to do it properly. The days will come, when the bridegroom is taken away from them, and then they will fast. (Matt 9:15)
To be effective fasting must center on God. As we fast we discover the things that control us. David writes, “I humbled my soul with fasting (Ps 69:10).” Fasting reminds us that it is not food that sustains us, but God. It also helps us develop the discipline that is necessary for our spiritual growth.
Our spiritual condition is fallen and the demands of the body reign over the soul for most of us. The challenge is to liberate the soul and give it strength to be in charge of our actions, to become freed from the programmatic responses of our brain which is a bodily function. When we feel hunger, this is a body demand. We almost automatically succumb to its demand without thinking. When we fast we put our soul in charge and choose to overcome the pangs of hunger for the glory of God. This action is an act of the soul. This is how fasting helps develop the strength of our soul. Since hunger is such a basic human need and something we must do often, and one that we frequently overindulge in, fasting is one of the first disciplines taught to build the strength of our soul. After conquering this bodily demand then it is easier to conquer the other lusts. For this reason our Church Fathers teach the primary importance of fasting as apart of our spiritual discipline. But we do so recognizing that fasting is not a virtue. It is means to strengthen the power of our soul so we can act more closely to the will of God. It is a pathway to a virtuous life and our union with God.
The Church in her wisdom and for the benefit of our spiritual growth has provided for us fasting periods. These are times through out the year where we can focus on our spiritual life and double our efforts in prayer and worship.
On the outward level fasting involves physical abstinence from food and drink, and without such exterior abstinence a full and true fast cannot be kept; yet the rules about eating and drinking must never be treated as an end in themselves, for ascetic fasting always has an inward and unseen purpose. Man is a unity of body and soul, 'a living creature fashioned from natures visible and invisible.' Our ascetic fasting should therefore involve both these natures at once. The tendency to over-emphasize external rules about food in a legalistic way, and the opposite tendency to scorn these rules as outdated and unnecessary, should be rejected. In both cases the proper balance between the outward and the inward has been impaired.
Fasting is not a mere matter of diet. It is moral as well as physical. In the words of St. John Chrysostom, it means “abstinence not only from food but from sins”. “The fast”, he insists, “should be kept not by the mouth alone but also by the eye, the ear, the feet, the hands and all the members of the body”: the eye must abstain from impure sights, the ear from malicious gossip, the hands from acts of injustice. It is useless to fast from food, protests St. Basil, and yet to indulge in cruel criticism and slander: “You do not eat meat, but you devour your brother”.