The disciples asked the Lord why they could not heal an Epileptic boy. Jesus said,

“Because of your unbelief... However, this kind does not go out except by prayer and fasting” (Matthew 17:14-21).

Faith needs prayer for its development and full growth, and prayer needs fasting for the same reason.  Faith needs prayer for its development and full growth, and prayer needs fasting for the same reason. Fasting has done wonders when used in combination with prayer and faith. This is a biblical doctrine.

TO FAST MEANS TO ABSTAIN FROM FOOD

To fast means to abstain from food—that which caused the fall of man.

Fasting

• humbles the soul before God (Psalm 35:13); 
• chastens the soul (Psalm 69:10); 
• and crucifies the appetites and denies them so as to give the entire time to prayer (2 Samuel 12:16-23; Matthew 4:1-11). 
• It manifests earnestness before God to the exclusion of all else (1 Corinthians 7:5); 
• shows obedience; 
• Gives the digestive system a rest (Matthew 6:16-18; 9:15; Luke 5:33); 
• demonstrates the mastery of man over appetites; 
• aids in victory over temptation; 
• helps to attain power over demons; 
• develops faith; 
• crucifies unbelief; 
• and empowers prayer (Matthew 4:1-11; 17:14-21). 

ALL BELIEVERS ARE SUPPOSED TO FAST

All believers are supposed to fast, but no regulations or set rules are given as to how long or how often. That is determined by individual desire and need (Matthew 9:14-15; 1 Corinthians 7:5; Acts 13:1-5).

WHEN SHOULD YOU FAST ?

Men should fast when

• under chastening (2 Samuel 12:16-23); 
• under judgment (1 Kings 21:27); 
• in need (Ezra 8:21); 
• in danger (Esther 4); 
• when worried (Daniel 6:18); 
• in trouble (Acts 27:9, 33); 
• in spiritual conflict (Matthew 4:1-11); 
• and when desperate in prayer (Acts 9).