For answers to prayer: "We fasted and prayed to our God for this, and our petition was granted" (Ezra 8:23). Burdened with embarrassment about having to ask the Persian king for an army to protect him and his fellow travelers, Ezra fasted and prayed, and the king granted his request.
For forgiveness of sin: "When they were gathered at Mizpah, they drew water and poured it out on the ground before the Lord, and they fasted that day, confessing, ‘We have sinned against the Lord’" ?(1 Samuel 7:6). Samuel led God’s people in a fast to celebrate the return of the Ark of the Covenant and to pray that Israel might be forgiven of the sin that allowed the Ark to be captured in the first place.
For clarity and guidance: "Saul got up from the ground, but when he opened his eyes he could see nothing; so they led him by the hand and brought him to Damascus. For three days he was unable to see, and he neither ate nor drank" (Acts 9:8-9). Having just experienced a traumatic conversion, Paul fasted for three days while he tried to reconcile himself to the fact that he had been wrong to persecute the Christians. After three days, he was visited by Ananias, a Christian leader in Damascus, who prayed over him, restored his eyesight, and helped him gain clarity on God’s calling for him.
For a special calling or mission: "He will be great in the sight of the Lord. He will drink neither wine nor strong drink. He will be filled with the Holy Spirit even from his mother’s womb" (Luke 1:15). John the Baptist adopted a rigorous fast to help keep him focused on his ministry.
Appeal to God for protection: "Fast on my behalf, all of you, not eating or drinking, night or day, for three days. I and my maids will also fast in the same way. Thus prepared, I will go to the king" (Esther 4:16). It was against the law for a woman to appeal to the king in Babylon. But Esther dared to do this so that she could plead with the king to protect her people from destruction. Prior to taking this bold step, Esther asked all the Jews to fast and pray that God would protect her. The king welcomed her, heard her petition, and saved the Jews.