Fasting is a spiritual discipline that is observed in countless churches worldwide. We hear about corporate (churchwide) fasts, 21-day challenges, 40-day “give-up-one-thing” fasts, the Daniel fast, the “Jewish” 3-day fast, and countless other types of fasts.

Maybe you, like me, have participated in many of those fasts over the years, but you were never really clear about biblical fasting. You aren’t alone.

Biblical fasting isn’t something we should take lightly. So before we make the commitment to fast, we need to ask ourselves two important questions:

What is a biblical fast?
Does God approve of every fast we enter into?

Many are confused but want to be obedient in this area. Sadly, many man-made traditions have been given equal authority with God’s Word and have kept the discouragement and misunderstandings going strong through the years. Too often we fast because we are expected to (religion), not because our hearts long to draw closer to God (relationship).

This is such an important topic because what God has to say on a subject is far more important than anything a man has to say about it. God is our ultimate authority. Long before fasting became a modern-day experience, God had already spoken about it.

What is True Biblical Fasting That is Acceptable to God?

A definition for biblical fasting is not found in Scripture. However, Scripture interprets Scripture. In this case, the Bible contains over fifty references to fasting that we can learn from. When we put these verses together, we have a framework that shows us what biblical fasting is.

Biblical fasting is a voluntary setting aside of something we desire (usually food) for a period of time to seek God more intentionally. It focuses our attention, replaces physical comforts with reliance on God, and directs our prayers.

In defining biblical fasting, I found the two most revealing passages come from Isaiah 58 and Matthew 6:16-18. In these passages, the Lord pulls back the veil to show us the boundaries for acceptable and not acceptable fasting. If we are willing to sit with these verses, they will refine our understanding and break the spiritual bondages that God wants to set us free from.

Something we may not want to examine too closely–but must–is this: it is entirely possible to fast and miss God’s heart. Not because we didn’t last long enough. Not because we drank coffee instead of water. But because fasting, at its core, has never been about our performance.

That thought should make us pause, ask questions, grab our Bible, and check our hearts. It sure hit me hard.

Fasting in Isaiah 58 Explained

Another time I will break down both Isaiah 58 and Matthew 6 verse by verse. But for today’s post, we will hit the highlights.

Isaiah 58 opens with God’s people regularly practicing fasting. They truly believed they were fasting correctly. They seemed to seek God daily and delighted to know His ways. They felt they did all the right things.

Yet, God did not answer their prayers. They were angry about that and felt that He was ignoring them in their times of need.

God told Isaiah to confront them about their fasting and their complaints because he was not pleased. God said they were going through the motions to seek Him and their outward piety masked unchanged hearts. This displeased the Lord.

God wasn't upset with them because they abstained from food incorrectly. He didn’t even address the food they ate or how they fasted. He was upset with them because their fasts were shallow, empty religious rituals without heart change. See, it was their hearts and how they treated others that mattered to God, not the sacrifices they made.

Fasting in Matthew 6:16-18 Explained

First of all, in this passage Jesus said, “when you fast,” not “if you fast.” So Jesus expected us to fast while He (our bridegroom) was away. Then, He addressed the boundaries we need to abide by during our time of fasting.

Because context matters, we need to understand that throughout Matthew 6, Jesus tells us how to live a godly life by combining four spiritual disciplines: giving, praying, forgiving, and fasting so that our treasures will be found in heaven, not sought on earth. He gives us wisdom in each of those areas and then wraps up the chapter by telling us what to do when worry and anxiety overtake us.

On the surface, it might seem that Jesus randomly threw fasting in the middle of that spiritual pile. But each of those 4 disciplines have a purpose; they strengthen our relationship with the Father and each other and helps us move away from greed, pride, and selfish indulgences to be more like Jesus.

God wants us to be careful not to do the right things for the wrong reasons, such as fasting in a way that draws attention and praise from others instead of fasting discreetly so that only Father God sees. Jesus advised that we go about our self-care and allow our day to be as normal as possible. True fasting is about heart change and reshapes how we live before others.

Both Isaiah and Jesus make the same point: fasting without heart transformation is empty–and God does not accept it. The issue isn’t abstaining from food. The heart of the matter is misaligned motives.

The Fruit Fasting Is Meant to Produce

Both passages in Isaiah and Matthew show us that the purpose of biblical fasting is to turn to God and bare our hearts before Him.

God uses our time of fasting to teach us more about Himself, to expose and correct wrong teaching we have accepted as truth, to strengthen us to obey Him, and to encourage righteous living because it affects others. God wants to see transformation in our hearts that produces lasting, godly fruit. We can’t do it alone. That is why fasting with prayer is such a powerful combination!

Wrapping Things Up

God means what He says and says what He means. In Isaiah 58 and Matthew 6, He lovingly shows us that fasting is never about impressing others or performing for Him. It is about drawing near with sincerity, humility, and a heart willing to be changed.

God will not accept superficial worship or hollow rituals. But He gladly receives the humble heart that seeks Him in truth. Unacceptable fasting in Scripture is about wrong motives–not human limitations.

And that distinction matters.

Because while Scripture warns against shallow, self-centered fasting, it never labels the sincere believer who struggles as a failure. We will talk more about that in our next post.

A Few Journal Prompts for a Gentle Next Step

The prompts below reflect a practice God has used in my spiritual walk – Bible notebook journaling. The prompts are not meant to be completed all in one sitting. When you next sit down with God, choose a prompt that resonates with you and allow yourself the freedom to linger with God as long, or as briefly, as He leads. Record your reflections in your Bible or in a notebook. If you are curious but unfamiliar with Bible notebook journaling, you can read more about it here.

What is your heart actually hungry for? Isaiah 58 describes people who fasted religiously but whose hearts were far from God’s purposes. When you fast (or think about fasting), what are you truly longing for–is it a spiritual experience, God’s approval, a sense of control, or something else? What does that hunger reveal about where you are with God right now?
What would it look like to fast from something other than food? Isaiah 58 paints a picture of fasting as a transformation of your life, not just the appetite. Is there something else in your life (scrolling, busyness, complaining, gossiping, people-pleasing) that, if you stepped back from it, might create the same kind of sacred space that food fasting is meant to create? What has God been quietly nudging you toward laying down at His feet?
Where is the “loose the chains” moment in your life? Isaiah 58 and Matthew 6 talk about true fasting as loosening the chains of bondage, living a godly life that blesses others, and setting the oppressed free. Who in your life (a person, a relationship, a community) might God be calling you to show up for as an act of fasting?
Who are you fasting for? Matthew 6:16-18 warns against fasting to be seen by others. But this can be subtle. Maybe it’s not a church full of people you are trying to impress but an audience of one (maybe even to prove something to yourself). When you picture yourself fasting, whose face comes to mind?

I also include journaling prompts in my monthly emails as a way to encourage Bible notebook journaling throughout the month. I have found it is a great way to train your mind to think biblically.

If this practice of Bible journaling isn’t right for your walk with Christ, feel free to skip it. The prompts are simply offered as a gift from my heart to yours.