Although the connection between prayer and fasting is not specifically explained in Scripture, a common thread connecting the two seems to run through all the instances of prayer and fasting recorded in the Bible. In the Old Testament, it appears that fasting with prayer had to do with a sense of need and dependence, and/or of abject helplessness in the face of actual or anticipated calamity. Prayer and fasting are combined in the Old Testament in times of mourning, repentance, and/or deep spiritual need.

The first chapter of Nehemiah describes Nehemiah praying and fasting, because of his deep distress over the news that Jerusalem had been desolated. His many days of prayer were characterized by tears, fasting, confession on behalf of his people, and pleas to God for mercy. So intense was the outpouring of his concerns that it’s almost inconceivable he could “take a break” in the middle of such prayer to eat and drink. The devastation that befell Jerusalem also prompted Daniel to adopt a similar posture: “So I turned to the Lord God and pleaded with him in prayer and petition, in fasting, and in sackcloth and ashes” (Daniel 9:3). Like Nehemiah, Daniel fasted and prayed that God would have mercy upon the people, saying, “We have been wicked and have rebelled; we have turned away from your commands and laws” (v. 5).

In several instances in the Old Testament, fasting is linked with intercessory prayer. David prayed and fasted over his sick child (2 Samuel 12:16), weeping before the Lord in earnest intercession (vv. 21-22). Esther urged Mordecai and the Jews to fast for her as she planned to appear before her husband the king (Esther 4:16). Clearly, fasting and petition are closely linked.

There are instances of prayer and fasting in the New Testament, but they are not connected with repentance or confession. The prophetess Anna “never left the temple but worshiped night and day, fasting and praying” (Luke 2:37). At age 84, her prayer and fasting were part of her service to the Lord in His temple as she awaited the promised Savior of Israel. Also in the New Testament, the church at Antioch was fasting in connection with their worship when the Holy Spirit spoke to them about commissioning Saul and Barnabas to the Lord’s work. At that point, they prayed and fasted, placed their hands on the two men and sent them off. So, we see in these examples that prayer and fasting are components of worshipping the Lord and seeking His favor. Nowhere, however, is there any indication that the Lord is more likely to answer prayers if they are accompanied by fasting. Rather, fasting along with prayer seems to indicate the sincerity of the people praying and the critical nature of the situations in which they find themselves.

The more critical the situation, the more appropriate the fasting and prayer. In Mark 9, Jesus casts a demon from a boy. The disciples had been unable to perform the exorcism, although they had previously been given authority over unclean spirits (Mark 6:7). Later, the disciples asked Jesus why they failed in their attempts to free the boy from the demon, and Jesus said, “This kind can come out only by prayer” (Mark 9:29). Matthew’s account adds the phrase “and fasting” (Matthew 17:21). In this particular case, the demon was exceptionally malicious and obdurate (Mark 9:21-22). Jesus seems to be saying that a determined foe must be met with an equally determined faith. Prayer is a ready weapon in the spiritual battle (Ephesians 6:18), and fasting helps to focus prayer and give it resolve.

The theology of fasting is a theology of priorities in which believers are given the opportunity to express themselves in an undivided and intensive devotion to the Lord and to the concerns of spiritual life. This devotion will be expressed by abstaining for a short while from such normal and good things as food and drink, so as to enjoy a time of uninterrupted communion with our Father. Our “confidence to enter the Most Holy Place by the blood of Jesus” (Hebrews 10:19), whether fasting or not fasting, is one of the most delightful parts of that “better thing” which is ours in Christ. Prayer and fasting should not be a burden or a duty, but rather a celebration of God's goodness and mercy to His children.

Isaiah 58:1-12 True and spurious fasting. Loudly, with all the strength of throat and as with trumpet-voice, the prophet is to cry and denounce the rebellion and the sins of the people. I. THEIR FORMALITY AND HYPOCRISY, They consult Jehovah daily; they apply to the prophet or the oracle; they offer prayer. They profess to desire to know God's ways, his commands, and his dealings with his people. Just as if they were a holy people, and were not really far in heart from God, they demand of him "judgments of righteousness;" ie manifestations of his pleasure as the God of the covenant, his approach as the God of justice. They adhered to the forms of religion, but the heart was not in them. Relying on those forms, they were surprised the Divine favour was not vouchsafed to them "A hypocrite has no true and real delight in the service of God or in his truth; but, at the same time, there may be a great deal of professed interest in the ways of God. A great deal of busy and bustling solicitude about the order of religious services, the external organization of the Church, the ranks of a clergy, the claims of a liturgy. There may be a great deal of pleasure in theological discussion, in the metaphysics of theology, in the defence of what is deemed orthodoxy. There may be much pleasure in the music of devotion, in the pleasant voice of a preacher, in the triumphs of party, the advancement of our sect. But true religion is delight in religion itself—in the service of God as such, and because it is holy. It is pleasure, not even in the triumph of Christianity as a mere party measure, but in God as he is, his holy service and truth" (Barnes).

SPURIOUS FASTING. Formal fasting appears to have increased from the time of the Captivity. Another phrase for it was "humbling the soul" (Le 16:29, 31; 23:27, 32; Numbers 29:7; Numbers 30:13). In connection with this outward observance, they keenly pursue business ends, exacting the full tale of tasks "Like Shylock, they demand the pound of flesh, at the same time that they may be most precise, punctual, and bigoted in the discharge of the duties of religion. If we desire to keep a fast acceptable to God, it should be such as shall make us kind, mild, benignant; such as shall take effect in the unbinding heavy burdens from the poor, and relaxing the rigidness of the claims we have on others" Moreover, the fasting is connected with strife and contention; and so their prayers cannot rise to the seat of Jehovah (Isaiah 57:15) "Thou hast covered thyself with clouds, so that prayer may not pass through" (Lamentations 3:44) "Their words fly up, their thoughts remain below; Words without thoughts never to heaven go" The inclination of the head, the sackcloth and the ashes,—these make not the fast in the eyes of Jehovah "It is not a mournful expression, a solemn dress, or a thin table that God so much regards. It is the heart, and not the stomach, that he would have empty; and, therefore, if a man carries a luxurious soul in a pining body, or the aspiring mind of a Lucifer on the hanging head of a bulrush, he fasts only to upbraid his Maker, and to disgrace his religion, and to heighten his final reckoning, till he becomes ten times more the son of perdition than those who own their inward love of sin by the open undissembled enmities of a suitable behaviour. Let a man not count himself to have fasted to any purpose, if by it he has not got ground of his corruption, in some measure supplanted his sin, and estranged his affections from the beloved embraces of sinful objects" (South)