What Is Biblical Fasting and Why Do We Fast?

Before we journey through Scripture to see how God's people have fasted across centuries, we need to understand what fasting actually is and what the Bible reveals about its fundamental purpose. This week lays the foundation for everything that follows.

At its core, fasting in Scripture means voluntarily abstaining from food—and sometimes other things—for a spiritual purpose. It is not simply going without a meal because you are busy or because you are dieting for health reasons. Biblical fasting is always intentional and always connected to your relationship with God. When someone in the Bible fasted, they were setting aside normal activities and comforts to focus wholly on seeking God, confessing sin, grieving loss, or interceding for others. The physical emptiness created by fasting becomes a mirror for the soul: you feel your hunger and thirst, and you let that physical sensation turn your heart toward God.

The word most commonly translated "fast" in the Old Testament is the Hebrew word tsuwm, which means simply to abstain from food. In the New Testament, the Greek word is nesteia, with the same basic meaning. But the Bible never treats fasting as merely physical. A passage in Isaiah reveals something crucial about this. The prophet describes people who fasted, keeping the spiritual disciplines outwardly, yet their hearts remained far from righteousness. God tells them that this kind of fasting—going through the motions without a genuine heart change—accomplishes nothing (Isaiah 58:1-7). True biblical fasting must always involve the whole person: body, mind, and spirit united in seeking God's face.

So why do God's people fast? Scripture shows us several key reasons woven throughout the biblical narrative.

First, fasting often accompanies repentance and confession of sin. When people recognize their wrongdoing before God, fasting expresses the seriousness and depth of their sorrow. It is an outward sign that they are genuinely turning away from sin and turning back to God. The physical sacrifice mirrors the inner reality: I am giving up what I want and what is comfortable because I recognize the gravity of what I have done and my desperate need for God's forgiveness. This connection between fasting and repentance appears repeatedly throughout Scripture, and we will examine it more closely in Week 2.

Second, fasting is a tool for seeking God's guidance and intervention. When people faced crucial decisions or urgent needs—when they did not know what to do and felt wholly dependent on God—they often fasted as part of their prayer. The absence of food helped them set aside distractions and dedicate themselves completely to seeking God's will or asking for His help. They were saying through their bodies: "I need God more than I need food. This matter is that serious."

Third, fasting can express grief and mourning. When facing loss or tragedy, God's people sometimes fasted as a way of outwardly expressing their inner sorrow and their sense of helplessness before circumstances they could not control. Again, the physical emptiness matched the emotional emptiness they felt.

Fourth, fasting appears connected to spiritual warfare and prayer that seeks God's power. When believers prayed for God to act in situations of spiritual significance—when they felt they were battling against spiritual darkness or seeking God's miraculous intervention—fasting sometimes accompanied those prayers. The sacrifice and focus fasting created made room for extraordinary prayer.

Now, here is something vital to understand from the very beginning: nowhere in Scripture is fasting commanded as a regular, required practice for all believers. This is important. God gave His people the Law with many specific commands, and regular fasting was never listed among them as an obligation. When fasting appears in the Old Testament, it is often in response to specific circumstances—a national crisis, personal sin, grief, or a particular need. The one exception is the Day of Atonement, where the Law commanded the people to "afflict yourselves," which was understood to include fasting (Leviticus 16:29). But even here, this annual observance was distinct and set apart.

In the New Testament, Jesus acknowledges that His disciples will fast—but His language is striking. In Matthew 9:15, when people ask Him why His disciples do not fast while John's disciples and the Pharisees do, Jesus replies that the time will come when the bridegroom is taken from them, and then they will fast. He does not command them to fast; He simply predicts that they will. The early church did practice fasting, as we will see in Week 4, but it remained a voluntary spiritual discipline, not a requirement.

This freedom matters deeply because it protects us from a danger that Jesus Himself warned against. The Pharisees of His day had turned fasting into a law and a measure of spiritual superiority. They fasted twice a week and made sure everyone knew about it (Luke 18:12). Jesus made clear that this kind of fasting—done for show and rooted in pride—actually distances us from God rather than drawing us closer. That is why Week 6 of this course focuses specifically on guarding against legalism and pride when we fast. Fasting can become deeply unhealthy spiritually if we misunderstand it or misuse it.

Yet the very fact that fasting is voluntary and unrequired does not make it unimportant. Throughout Scripture, the godliest people—those closest to God and most serious about their relationship with Him—practiced fasting. It appears in the lives of prophets, apostles, and Jesus Himself. It is presented as something believers may do, should know how to do, and will find spiritually powerful when done with a right heart. The key is that it flows from genuine hunger for God, not from external pressure or a desire to appear righteous.

So here is what we will do in the weeks ahead. We will look at how fasting actually functioned in people's lives across Scripture—how they fasted, when they fasted, and what God revealed about the practice through His Word. We will see fasting in times of national disaster, personal repentance, and urgent spiritual need. We will hear Jesus's own teaching on fasting and see how He modeled it. We will examine the early church's practice and understand what different types of fasts meant. And finally, we will focus carefully on the matters of the heart, making sure that if we fast, we fast in a way that actually draws us closer to God rather than further away.

But first, we must settle one more foundational truth. Fasting in Scripture is never about earning God's favor or proving our worthiness to Him. It is not a way to twist God's arm or force Him to do what we want. Rather, fasting is a way of aligning ourselves—body and soul—with what we already believe to be true: that God is supremely valuable, that we need Him desperately, and that no comfort or satisfaction this world offers compares to knowing and serving Him. When we fast, we are not changing God's mind; we are changing our own hearts and opening ourselves to what God wants to do in us and through us.

With this foundation in place, we are ready to walk through Scripture and see what the practice of fasting teaches us about seeking God with our whole selves.