Fasting is a concept found scattered throughout the Bible and is the voluntary abstaining from all food for a set period of time. The Bible only refers to fasting in relation to food, never to fasting from things or favorite activities. This does not mean Scriptures do not discuss forsaking possessions or temporarily abstaining from specific activities, but it never refers to such self-denials as a fast. Only the refraining from food for a brief time is identified as fasting.
In discussing the question of fasting, it is important to note the Bible nowhere commands Christians to fast. In Matthew 6 and 9 Jesus assumes His followers will fast, but neither He nor any of the apostles every command fasting. Fasting is a voluntary abstaining from food for a spiritual purpose.
Biblical fasting is not for weight loss, internal cleansing or some other physical purpose. Fasting serves a spiritual purpse, but it is not some kind of spiritual hunger strike. One does not fast as a way of getting extra spiritual power or to twist God’s arm into granting a specific request. The Bible only gives a limited amount of information about fasting and does not give us any specific instructions that detail the purpose of fasting. This lack of detailed direction does not mean we are left to our own speculation. The information about fasting found in the Bible provides a clear picture of the attitudes that should motivate fasting.
The Old Testament exclusively refers to fasting in times of intense sorrow and suffering. The Israelites fasted in mourning during times of death, in preparation for battle it seemed the nation was doomed to lose and in grief over their sin. The vast majority of Biblical references to fasting are found in the Old Testament and all of them are directly related to deep sorrow.
The New Testament references to fasting are very few. Aside from passing references to people who fasted, the instructive examples of fasting in the New Testament can be summed up in three categories. Jesus rebuked the Pharisees for their public displays of fasting and taught His disciples to fast in secret. Jesus fasted for forty days in the wilderness at the beginning of His public ministry. The third category of fasting is that which took place when men were appointed to leadership positions in the church.
The two kinds of positive examples of fasting in the New Testament have one thing in common. Fasting took place at the beginning of serious, life threatening Christian ministry. Of course, Jesus ministry was life threatening, since it was destined to end in His death on the cross. The ministry to which Paul and Barnabas were commissioned in Acts 13 was a ministry that would lead to them into the face of intense persecution, physical suffering and personal loss. The elders put in place over the churches in Acts 14 were stepping into ministry leadership in the middle of communities which had already shown themselves to be violently opposed to the preaching of Jesus. Fasting in the New Testament has a direct connection to God’s servants stepping out into dangerous ministry.
The Bible seems to offer one uniform picture of fasting. Fasting is a response of deep sorrow. It seems to most often be a reflection of deep sorrow for sin or loss. The conclusion to be drawn from the examples of fasting in the Bible is that fasting is an expression of a desperate longing for God’s protection and direction in times of sin or great difficulty.
Everlasting Truths 
Maybe Jesus expected us to fast when in earnest prayer… he said in Matthew 6:17-18 “But you, when you fast, anoint your head and wash your face, so that you do not appear to men to be fasting, but to your Father who is in the secret place; and your Father who sees in secret will reward you openly.” Not a command, but maybe a suggestion?
That passage in Matthew 6 and Matthew 9:15 show Jesus had a clear expectation that His disciples would fast. Not commanded, but definitely assumed and anticipated. At times the sorrows of life and struggles with sin will drive the Christian earnest prayer and fasting.
Wasn’t Jesus a practicing Jew and fasted? Are we suppose to follow Jesus examples? Didn’t Jesus say “I have not come to abolish the Law, but to fullfill it. “? Just thinking.
Good questions! Yes, Jesus did fast and He would have fasted at all times commanded by the Law. The law of Moses only commanded one time of fasting for the Israelites, on the Day of Atonement (Leviticus 23:27). Jesus, as the fulfillment of the law, did away with the sacrifices and temple worship. We are as obligated to keep the law of fasting today as we are to sacrifice sheep in Jerusalem. We certainly are not required to imitate Jesus in every detail of His life. (Else, we should all be homeless, spending our time traveling the countryside with a dozen Galileans.) We imitate Jesus in those specifics in which it is commanded of us. Fasting is one of those good areas that is voluntary and helpful for the Christian, but not required.