I read about Ezra, how he lead a group of Jews from Babylon back to Jerusalem. 'Then I proclaimed a fast...before our God, to seek of him a right way for us, and for our little ones...So we fasted and besought our God for this; and he was intreated of us.' (Ezra 8:21 & 23).
I read about Nehemiah and his concern for the Jews in Jerusalem, that he 'sat down and wept, and mourned certain days, and fasted, and prayed before the God of heaven' for their welfare.
In the book of Esther I read about her request that all of the Jews fast for three days that she might find favor in the sight of the king and save her people. (Esther 4:16)
Next I read about king Darius who 'passed the night fasting' when Daniel was cast into the den of lions. (Daniel 6:18)
I found a beautiful passage in Joel 2:12-13 where the LORD invites '...turn ye even to me with all your heart, and with fasting, and with weeping, and with mourning: And rend your heart, and not your garments, and turn unto the LORD your God...'
In the New Testament I read about the Savior teaching his disciples that fasting and prayer are indispensable requirements to do His work. (Matt 17:21)
In the Book of Mormon I read Alma's powerful declaration as he taught about repentance, obedience, being born again and cleansed through the blood of Christ: ' Behold, I have fasted and prayed many days that I might know these things of myself that they are true...' (Alma 5:46) And in Alma 17:3 we learn why the sons of Mosiah had such amazing missionary experiences, '...they had searched the scriptures diligently, that they might know the word of God...they had given themselves to much prayer, and fasting; therefore they had the spirit of prophecy, and the spirit of revelation, and when they taught, they taught with power and authority of God.'