The short answer
In the Bible, fasting means voluntarily going without food for a set time in order to seek God more earnestly in prayer. It is the deliberate setting aside of a physical appetite so that a spiritual one can take priority. Scripture is full of it — in grief, in repentance, in urgent intercession, and in preparation for God's great tasks. The prophet Joel voices its heart: “Even now, declares the Lord, return to me with all your heart, with fasting and weeping and mourning” (Joel 2:12). Fasting is not about the food; it is about turning the whole self toward God.
The Bible does not present fasting as a legal requirement that condemns those who neglect it, yet it plainly assumes believers will practice it. Jesus said “when you fast,” not “if you fast” (Matthew 6:16). Understood rightly, fasting is one of the ways we humble ourselves, express our dependence on God, and show — to him and to ourselves — that we are serious about drawing near. This article looks at what fasting is, why people fast throughout Scripture, the striking role of the number forty, how Jesus taught us to fast, and how fasting functions as a condition of sincere devotion.
What fasting is in Scripture
Biblical fasting is primarily abstaining from food for a spiritual purpose, coupled with prayer. The word carries the sense of humbling or afflicting oneself — David wrote, “I humbled myself with fasting” (Psalm 35:13). It is a bodily way of saying with our whole being that we hunger for God more than for bread. By stepping back from something as basic as eating, we create space to focus, to pray, and to feel our own smallness and need before the One who sustains us. The empty stomach becomes a kind of prayer in itself, a continual reminder to turn Godward.
Scripture describes fasts of varied length and form. There are single-day fasts, the three-day fast of Esther and her people (Esther 4:16), the week of mourning at Saul's death (1 Samuel 31:13), and the extraordinary forty-day fasts of Moses, Elijah, and Jesus. Some were private; some were called for a whole community, as when Judah proclaimed a fast to seek the Lord in danger (2 Chronicles 20:3). What unites them is not a technique but a posture — a heart deliberately humbled and directed toward God. Fasting naturally belongs alongside prayer, its constant companion; the two together are explored further in what prayer is and how we pray.
Why people fast in the Bible
People fast in Scripture for several clear reasons, and the deepest is always the same: to humble themselves and draw near to God. One great purpose is repentance. When Joel called Judah back to God, he called them to fast; when Nineveh heard Jonah's warning, the whole city fasted in sorrow for its sin (Jonah 3:5). Fasting gives grief over wrongdoing a bodily voice, embodying a turning of the heart that mere words might leave shallow. It is a way of saying to God that we mean our repentance.
Fasting also accompanies urgent prayer and important decisions. Before sending out Paul and Barnabas, the church at Antioch was “worshiping the Lord and fasting” when the Holy Spirit gave direction, and they “fasted and prayed” again before commissioning them (Acts 13:2–3). Esther asked her people to fast for three days before she risked her life for them (Esther 4:16). In danger, in mourning, in intercession for others, and in seeking God's guidance, believers turned to fasting to focus their whole attention on God and to express dependence on him rather than on their own resources. In every case fasting is not a way to twist God's arm but a way to align our hearts with his.
Fasting the number 40 keeps marking
One of the most striking patterns in Scripture is the recurrence of forty-day fasts at pivotal moments of God's work. Moses was on the mountain with God “forty days and forty nights” without eating or drinking as he received the covenant (Exodus 34:28). Elijah, fleeing and despairing, traveled “forty days and forty nights” on the strength of God's provision to meet him at Horeb (1 Kings 19:8). And before beginning his ministry, Jesus “fasted forty days and forty nights” in the wilderness (Matthew 4:2), preparing to face temptation and to inaugurate his mission.
The repetition is not accidental. Across the Bible the number forty marks periods of testing, preparation, and transition — times set apart before something new begins. A forty-day fast, then, is not merely a long stretch of hunger; it is a season deliberately consecrated to God at a threshold moment. These fasts prepared their subjects to receive God's word, to be renewed, and to step into a calling. The pattern is worth pondering on its own, and it connects to a wider biblical rhythm traced in why the number 40 keeps appearing in the Bible. Fasting, in these moments, is the outward shape of a life pausing to be readied by God.
How Jesus taught us to fast
Jesus both fasted himself and taught his followers how to do it rightly, and his central concern was sincerity over performance. “When you fast, do not look somber as the hypocrites do, for they disfigure their faces to show others they are fasting… But when you fast, put oil on your head and wash your face, so that it will not be obvious to others that you are fasting, but only to your Father, who is unseen” (Matthew 6:16–18). The danger he named is turning a private act of devotion into a public display for admiration. Fasting done to be seen has already received its only reward.
Notice again that Jesus said “when you fast,” assuming the practice as a normal part of a believer's life, while directing it entirely toward God. He also indicated that fasting has its seasons: when asked why his disciples did not fast while he was with them, he replied that guests do not fast while the bridegroom is present, “but the time will come when the bridegroom will be taken from them; then they will fast” (Matthew 9:15). Fasting, then, is neither a badge to flaunt nor an empty ritual, but a sincere turning to God whose only intended audience is the Father who sees in secret and rewards accordingly.
Fasting as a condition of devotion
Seen across the whole of Scripture, fasting functions as a condition we set — a deliberate offering of self-denial that expresses and deepens our devotion to God. It is not that going hungry earns God's favor as a transaction; God's love is not for sale. Rather, fasting is a way of putting our whole self behind our prayers, of investing something real so that our seeking is not merely words. When we voluntarily give up a legitimate good for a time in order to concentrate on God, we make a tangible offering of the heart, and that kind of wholehearted turning is exactly what God honors.
This is why fasting so often appears at moments of repentance, preparation, and restoration in the biblical story. Setting a condition of devotion — laying something down to draw near to God — runs through Scripture's account of how broken things are made right, a theme explored in restoration through indemnity. Understood this way, fasting is less about the discomfort of hunger and more about the direction of the heart: a way of saying, with our appetite as well as our words, that God matters more than anything we might consume. Practiced sincerely and in secret, it remains one of the oldest and most personal ways believers have drawn close to their Creator.
Frequently asked questions
What is fasting in the Bible?
In the Bible, fasting means voluntarily going without food for a set time in order to seek God more earnestly in prayer — setting aside a physical appetite to concentrate on a spiritual one. Scripture records it in mourning, repentance, urgent prayer, and preparation for great tasks, always as a way of humbling oneself before God and depending on him rather than on our own strength.
Does the Bible command Christians to fast?
The Bible does not issue fasting as a universal command the way it commands love or honesty, but it clearly assumes believers will fast. Jesus said “when you fast,” not “if you fast” (Matthew 6:16), treating it as normal devotion. Fasting is presented as good, profitable, and expected of those who seek God, rather than as a legal requirement whose absence condemns.
Why do people fast in the Bible?
People fast to repent of sin (Joel 2:12), to mourn, to seek God's guidance before a major decision (Acts 13:2–3), to intercede urgently for others (Esther 4:16), and to prepare for a great work. In every case the point is the same: humbling ourselves, turning our full attention to God, and showing that we are serious about our relationship with him.
How long should a fast last?
Scripture describes fasts of many lengths — a single day, three days, seven days, and the extraordinary forty-day fasts of Moses, Elijah, and Jesus. There is no fixed rule; the length should fit the purpose, one's health, and honest devotion rather than a wish to impress. Most believers begin modestly, and any extended fast should be undertaken thoughtfully and, where health is a concern, with medical guidance.
What did Jesus teach about fasting?
Jesus taught that fasting should be sincere and hidden, not a performance: “When you fast, do not look somber as the hypocrites do… but… wash your face, so that it will not be obvious to others” (Matthew 6:16–18). He assumed his followers would fast, but insisted the audience be God alone, promising that the Father who sees in secret will reward them.