What does the Bible say about Christian fasting?

from the old testament

• In Exodus 19:15, the Israelites abstained from sex for three days before their encounter with God at Mt. Sinai. Although the Israelites’ reasons for fasting in the book of Exodus are different from the reasons we fast today, we can abstain from sex (with the consent of our marriage partner) as a way to recenter our focus on God. Fasting from food or sex may help us better grasp our ultimate dependence upon God.
• When we fast, we must avoid doing it with sinful or self-serving motives, as described in Isaiah 58:3–7.
• Fasting was often connected to repentance, expressing a deep sorrow for sin and a desire to return to God wholeheartedly (Joel 2:12—13).
• The people of Nineveh fasted in response to Jonah’s warning, and God relented from destroying them (Jonah 3:5—10).
• Esther and the Jews fasted for three days before she approached the king. Fasting was used to seek God’s favor, protection, and courage in times of great danger and decision-making (Esther 4:16).
• Fasting served as a communal act of seeking God’s help and guidance in the midst of crisis in 2 Chronicles 20:3.
• Fasting was viewed as a form of self-humbling before God, an act of submission and dependence (Psalm 35:13).

from the new testament

• Fasting is a spiritual exercise in giving something up to express dependence on our Creator—-not an attempt to prove our allegiance to Him, or to show off our spirituality. Matthew 6:16-18 tells us, "And when you fast, do not look gloomy like the hypocrites, for they disfigure their faces that their fasting may be seen by others. Truly, I say to you, they have received their reward. But when you fast, anoint your head and wash your face, that your fasting may not be seen by others but by your Father who is in secret. And your Father who sees in secret will reward you."
• The New Testament does not actually command Christians to fast. However, the Bible does say fasting is a profitable and beneficial spiritual discipline. In the book of Acts, believers in the new church fasted together before making important decisions (Acts 13:2, 14:23). We can pursue communal fasting with other believers when making tough decisions as well.
• In Scripture, fasting is almost always done by abstaining from food. However, it is possible to fast in other ways. Anytime we give something up, temporarily, to focus exclusively on God and knowing Him and knowing His will, is good (1 Corinthians 7:1-5).

implications for today

Fasting is often combined with prayer, especially prayers of particular import (Luke 2:37, 5:33). The main purpose of fasting is not to hunger in a self-punishing way, but to increase one's focus on God. Fasting is meant to express to God, and to ourselves, that our relationship with Him is our main need and nourishment. When fasting, especially from food, it is wise to limit the time spent in the fast. In addition, it is important to consider that some people may not be able to fast from food, such as those with diabetes or other digestive disorders. God does not want us to harm or maim ourselves in an attempt to prove our allegiance to Him. Other variations of fasting outside of just eating no food—such as abstaining from sex, cutting out only certain food groups—and so on, are good. We know from Matthew 6:16-18 that the purpose for fasting is not for us to lord it over others or prove how much we are willing to suffer for God, but to grow closer to Him and experience the resultant peace and joy that is our reward.