The following is an excerpt from The MacArthur New Testament Commentary on Matthew 6.

But you, when you fast, anoint your head, and wash your face so that you may not be seen fasting by men, but by your Father who is in secret; and your Father who sees in secret will repay you. (6:17–18)Fasting is mentioned some thirty times in the New Testament, almost always favorably. It is possible that fasting was even overemphasized in some parts of the early church. At least four times a reference to fasting seems to have been inserted into the original text where it is not found in the earliest and best manuscripts (Matt. 17:21; Mark 9:29; Acts 10:30; 1 Cor. 7:5). The other favorable accounts, however, both in the gospels and in the epistles, show that proper fasting is a legitimate form of spiritual devotion.

Jesus’ statement when you fast (cf. Matt. 6:16) indicates that fasting is normal and acceptable in the Christian life. He assumes His followers will fast on certain occasions, but He does not give a command or specify a particular time, place, or method. Because the validity of the Day of Atonement ceased when Jesus made the once-for-all sacrifice on the cross (Heb. 10:10), the single prescribed occasion for fasting has ceased to exist.

Jesus’ disciples did not fast while He was with them because fasting is associated primarily with mourning or other times of consuming spiritual need or anxiety. When the disciples of John the Baptist asked Jesus why His disciples did not fast like they and the Pharisees did, He replied, “The attendants of the bridegroom cannot mourn as long as the bridegroom is with them, can they? But the days will come when the bridegroom is taken away from them, and then they will fast” (Matt. 9:14–15). Fasting is there associated with mourning.

Fasting is never shown in Scripture to be the means to heightened spiritual experience, visions, or special insight or awareness-as many mystics, including some Christian mystics, claim. Fasting is appropriate in this age, because Christ is physically absent from the earth. But it is appropriate only as a response to special times of testing, trial, or struggle.

Fasting is appropriate during times of sorrow. When God caused the first child born to Bathsheba by David to be taken ill, David fasted while he pleaded for the infant’s life (2 Sam. 12:16). He also fasted when Abner died (2 Sam. 3:35). David even fasted on behalf of his enemies. “When they were sick, my clothing was sackcloth; I humbled my soul with fasting; and my prayer kept returning to my bosom” (Ps. 35:13).

On such occasions of deep grief, fasting is a natural human response. Most people do not then feel like eating. Their appetite is gone, and food is the last thing they are concerned about. Unless a person is getting seriously weak from hunger or has some specific medical reason for needing to eat, we do them no favor by insisting that they eat.

Overwhelming danger often prompted fasting. King Jehoshaphat proclaimed a national fast in Judah when they were threatened with attack from the Moabites and Ammonites (2 Chron. 20:3). From a human standpoint they could not possibly win, and they cried out to God for help, forsaking food as they did so. Queen Esther, her servants, and all the Jews in the capital city of Susa fasted for three full days before she went before the king to plead for the Jews to be spared from Haman’s wicked scheme against her people (Esther 4:16).

As the exiles were about to leave Babylon for the adventurous return to Jerusalem, Ezra declared a fast, “that we might humble ourselves before our God to seek from Him a safe journey for us, our little ones, and all our possessions” (Ezra 8:21). Ezra continues, “For I was ashamed to request from the king troops and horsemen to protect us from the enemy on the way, because we had said to the king, ‘The hand of our God is favorably disposed to all those who seek Him, but His power and His anger are against all those who forsake Him.’ So we fasted and sought our God concerning this matter, and He listened to our entreaty” (vv. 22–23).

Penitence was often accompanied by fasting. David fasted after his double sin of committing adultery with Bathsheba and then having her husband Uriah sent to the front of the battle to be killed. Daniel fasted as he prayed for God to forgive the sins of his people. When Elijah confronted Ahab with God’s judgment for his great wickedness, the king “tore his clothes and put on sackcloth and fasted, and he lay in sackcloth and went about despondently” (1 Kings 21:27). Because of Ahab’s sincerity, the Lord postponed the judgment (v. 29). Centuries later, after the exiles had returned safely to Jerusalem, the Israelites were convicted of their intermarrying with unbelieving Gentiles. As Ezra confessed that sin in behalf of his people, “he did not eat bread, nor drink water, for he was mourning over the unfaithfulness of the exiles” (Ezra 10:6).

When the people of Nineveh heard Jonah’s preaching they were so convicted that they believed in God and “called a great fast and put on sackcloth from the greatest to the least of them. … By the decree of the king” they would “not let man, beast, herd, or flock taste a thing” (Jonah 3:5, 7). Rather than resent the warning of judgment and damnation, they repentantly turned to God and sought His forgiveness and mercy.

Fasting was sometimes associated with the receiving or proclaiming of a special revelation from God. As Daniel contemplated Jeremiah’s prediction of the seventy year’s desolation of Jerusalem, he gave his “attention to the Lord God to seek Him by prayer and supplications, with fasting, sackcloth, and ashes” (Dan. 9:2–3). As he continued “speaking in prayer,” he reports, “then the man Gabriel, whom I had seen in the vision previously, came to me in my extreme weariness about the time of the evening offering. And he gave me instruction and talked with me, and said, ‘O Daniel, I have now come forth to give you insight with understanding’ ” (vv. 21–22). A short time later, just before receiving another vision, Daniel made a partial fast-by forsaking “any tasty food, … meat or wine”-for three weeks (10:3). It is important to note that, though fasting was related to the revelations, it was not a means of achieving them. Daniel’s fasting was simply a natural accompaniment to his deep and desperate seeking of God’s will.

We often fail to understand God’s Word as fully as we ought simply because, unlike those great people of God, we do not seek to comprehend it with their degree of intensity and determination. Skipping a few meals might be the small price we willingly pay for staying in the Word until understanding comes.

Fasting often accompanied the beginning of an important task or ministry. Jesus fasted forty days and nights before He was tempted in the wilderness and then began His preaching ministry. Intensity and zeal over proclaiming God’s Word can so consume the mind and heart that food has no appeal and no place. Though abstaining from food has absolutely no spiritual value in itself, when eating is an intrusion on that which is immeasurably more important, it will be willingly, gladly, and unobtrusively forsaken.

Both before and after the Holy Spirit directed the church at Antioch to set apart Barnabas and Saul for special ministry, the people were praying and fasting (Acts 13:2–3). As those two men of God ministered God’s Word they prayed and fasted as they appointed elders in the churches they founded (14:23).

Only the Lord knows how much the leadership of the church today could be strengthened if congregations were that determined to find and follow the Lord’s will. The early church did not choose or send out leaders carelessly or by popular vote. Above all they sought and followed God’s will. Fasting has no more power to assure godly leadership than it has to assure forgiveness, protection, or any other good thing from God. But it is likely to be a part of sincere dedication that is determined to know the Lord’s will and have His power before decisions are made, plans are laid, or actions are taken. People who are consumed with concern before God do not take a lunch break.

In every scriptural account genuine fasting is linked with prayer. You can pray without fasting, but you cannot fast biblically without praying. Fasting is an affirmation of intense prayer, a corollary of deep spiritual struggle before God. It is never an isolated act or a ceremony or ritual that has some inherent efficacy or merit. It has no value at all-in fact becomes a spiritual hindrance and a sin-when done for any reason apart from knowing and following the Lord’s will.

Fasting is also always linked with a pure heart and must be associated with obedient, godly living. The Lord told Zechariah to declare to the people, “When you fasted and mourned in the fifth and seventh months these seventy years, was it actually for Me that you fasted? … Thus has the Lord of hosts said, ‘Dispense true justice, and practice kindness and compassion each to his brother; and do not oppress the widow or the orphan, the stranger or the poor; and do not devise evil in your hearts against one another’ ” (Zech. 7:5, 9–10). Seventy years of fasting meant nothing to the Lord, because it was done insincerely. Like the hypocrites that Jesus would later condemn, those Israelites lived only for themselves (v. 6).
After chastising the people in a similar way for their pretentious and unrighteous fasting, the Lord declared through Isaiah,  Is this not the fast which I chose, to loosen the bonds of wickedness, to undo the bands of the yoke, and to let the oppressed go free, and break every yoke? Is it not to divide your bread with the hungry, and bring the homeless poor into the house; when you see the naked, to cover him; and not to hide yourself from your own flesh? Then your light will break out like the dawn, and your recovery will speedily spring forth; and your righteousness will go before you; the glory of the Lord will be your rear guard. Then you will call, and the Lord will answer; you will cry, and He will say, “Here I am.” (Isa. 58:5–9)There can be no right fasting apart from a right heart, right living, and a right attitude.

But you, when you fast, Jesus tells those who belong to Him, anoint your head, and wash your face so that you may not be seen fasting by men. To anoint the head with oil was commonly done as a matter of good grooming. The oil was often scented and used partly as a perfume. Like washing the face, it was associated with day-to-day living, but especially with more formal or important occasions. Jesus’ point was that a person who fasts should do everything to make himself look normal and do nothing to attract attention to his deprivation and spiritual struggle.

The one who sincerely wants to please God will studiously avoid trying to impress men. He will determine not [to] be seen fasting by men, but by God the Father who is in secret. Jesus does not say we should fast for the purpose of being seen even by God. Fasting is not to be a display for anyone, including God. Genuine fasting is simply a part of concentrated, intense prayer and concern for the Lord, His will, and His work. Jesus’ point is that the Father never fails to notice fasting that is heart-felt and genuine, and that He never fails to reward it. Your Father who sees in secret will repay you.