This involves abstaining from all food, solid or liquid, but not from water. Jesus fasted in the wilderness when he was tempted by Satan. Luke 4:2, "...and in those days he did eat nothing."
This is a restriction of diet but not total abstention. The normal fast was the custom but the partial fast is seen in the restricted diet of vegetables and water of Daniel and his friends (Daniel 1:8-14) and in John the Baptists' diet of locusts and wild honey (Mark 1:6).
This fast is going without food and water. It usually appears as a desperate measure to meet a dire emergency. Esther called a three day fast of this type when she learned of the execution awaiting her and her people (Esther 4:16). The absolute fast is the EXCEPTION and should never be engaged unless one has a very clear command from God, and then for not more than three days.
IS FASTING A COMMANDMENT ?
No, but Jesus assumed that fasting would be a part of a person's devotional life. In the Sermon on the Mount He states, "when you fast, do not put on a gloomy face as the hypocrites do," (Matthew 6:16). Jesus did not say "If you fast," neither did He say "you must fast." He made the assumption that people would fast, and what was needed was instruction on how to do it properly.
THE PURPOSE OF FASTING
To intensify prayer efforts: Fasting simplifies our lives so that we are more able to focus on God. In fasting, we turn from a normal schedule and give ourselves to God in a consecrated way. It should draw us closer to God where we will experience a deeper relationship with Him.
To pursue holiness: Paul says, "Train yourself to be godly." (I Timothy 4:7 NLT). Fasting is one way to do that. It teaches us submission. It opens the spirit to the Lord because it quiets the flesh that is so often screaming for attention. Whatever is flesh-denying can also be character-forming.
To help us keep balance in our life: How easily we begin to allow nonessentials to take precedence in our lives. How quickly we crave things we do not need until we are enslaved by them (I Cor. 6:12). Fasting is not removing ourselves from the world but disciplining ourselves in the world; discipline brings freedom.
HOW TO HAVE A
Purify your motives. The purpose of a spiritual fast is to focus upon and worship God. We fast because we desire godliness and because we want God' s power to be seen in the church and in the world.
Begin gradually, perhaps with a partial fast. Many people find that beginning with a 24 hour fast from lunch to lunch (missing two meals) works well. Consume fresh fruit juices during this time. Replace your meal with your devotional readings and prayer. The most important thing to monitor is the inner attitude of worship.
Outwardly you will be performing the regular duties of your day, but inwardly you will be in ministry to the Lord through prayer, adoration, and song. The more you pray, the more you will feel sustained by God.
Progress to a 24 hour normal fast as the Lord gives you the grace to extend the time. Use only water and a healthy amount of it.
Fasting can have a powerful impact on your spiritual life. Consider a regular discipline of fasting one day a week for six months. Regular or weekly fasting had a profound effect in the lives of early church leaders.