On asceticism in general:
“And everyone who competes for the prize is temperate in all things. Now they do it to obtain a perishable crown, but we for an imperishable crown. Therefore I run thus: not with uncertainty. Thus I fight: not as one who beats the air. But I discipline my body and bring it into subjection, lest, when I have preached to others, I myself should become disqualified” (1 Cor. 9:25-27)
God calls us to turn to Him with fasting:
“‘Now, therefore,’ says the LORD, ‘Turn to Me with all your heart, with fasting, with weeping, and with mourning’” (Joel. 2:12)
The Lord Jesus Christ began His preaching with a fast:
“And when He had fasted forty days and forty nights, afterward He was hungry” (Matt. 4:2)
The Lord taught how to fast rightly:
“Moreover, when you fast, do not be like the hypocrites, with a sad countenance. For they disfigure their faces that they may appear to men to be fasting. Assuredly, I say to you, they have their reward” (Matt. 6:16)
“But you, when you fast, anoint your head and wash your face” (Matt. 6:17)
The disciples of the prophet John fasted:
“Then the disciples of John came to Him, saying, ‘Why do we and the Pharisees fast often, but Your disciples do not fast?’” (Matt. 9:14) (Mark. 2:18)
The disciples of Christ will fast after the crucifixion of Christ:
“And Jesus said to them, ‘Can the friends of the bridegroom mourn as long as the bridegroom is with them? But the days will come when the bridegroom will be taken away from them, and then they will fast’” (Matt. 9:15) (Mark. 2:20) (Luke. 5:35)
Some demons cannot be cast out of a person without fasting:
“However, this kind does not go out except by prayer and fasting” (Matt. 17:21) (Mark. 9:29)
A widow at the temple of the Lord served God with prayer and fasting night and day:
“a widow of about eighty-four years, who did not depart from the temple, but served God with fastings and prayers night and day” (Luke. 2:37)
An Angel was sent to the centurion during a fast:
“So Cornelius said, ‘Four days ago I was fasting until this hour; and at the ninth hour I prayed in my house, and behold, a man stood before me in bright clothing’” (Act. 10:30)
The Holy Spirit communicated with the first Christians during a fast:
“As they ministered to the Lord and fasted, the Holy Spirit said, ‘Now separate to Me Barnabas and Saul for the work to which I have called them’” (Act. 13:2)
The first Christians added fasting to prayer in every important matter:
“So when they had appointed elders in every church, and prayed with fasting, they commended them to the Lord in whom they had believed” (Act. 14:23)
For the sake of fasting spouses may temporarily abstain from each other:
“Do not deprive one another except with consent for a time, that you may give yourselves to fasting and prayer; and come together again so that Satan does not tempt you because of your lack of self-control” (1 Cor. 7:5)
In fasting the apostles show themselves as servants of God:
“But in all things we commend ourselves as ministers of God: in much patience, in tribulations, in needs, in distresses, in stripes, in imprisonments, in tumults, in labors, in sleeplessness, in fastings; by purity, by knowledge, by longsuffering, by kindness, by the Holy Spirit, by sincere love...” (2 Cor. 6:4-6)
The apostle, reproaching himself for forced self-praise (2 Cor. 11:21), boasts of fasting:
“in weariness and toil, in sleeplessness often, in hunger and thirst, in fastings often, in cold and nakedness” (2 Cor. 11:27)
The apostle allows Bishop Timothy to relax his fast because of poor health:
“No longer drink only water, but use a little wine for your stomach’s sake and your frequent infirmities” (1 Tim. 5:23)
A good deed = prayer + fasting + almsgiving + righteousness:
“Prayer with fasting is good, but better than both is almsgiving with righteousness. A little with righteousness is better than wealth with wrongdoing. It is better to give alms than to lay up gold” (Tob. 12:8)
King and prophet David in times of calamity humbled himself before God with fasting:
“But as for me, when they were sick, my clothing was sackcloth; I humbled myself with fasting; and my prayer would return to my own heart” (Ps. 35:13)