Moses fasted for many days. Awaken your minds, I entreat You, and lift them up at this opportune time, in company with Moses when he went up the mountain towards God. In this way may you start off afresh on your ascent, and be lifted up together with Christ, who did not merely go up a mountain but up to heaven, taking us with Him. Moses fasted for forty days on the mountain and according to the Scriptures he saw God, not darkly but face to face (Exod. 24:18). He talked to Him as someone would speak to his friend (Exod. 33:11, Deut. 34:10). He learnt from God and taught everyone about Him: that He is He Who eternally Is (Exod. 3:14) and will never cease to be, that He summoned what did not exist into existence, brought all things out of non-being and will not let them fall back into non-existence. In the beginning He brought the whole visible creation out of nothing all at once, just by a nod and His will. "In the beginning", it says, "God created the heaven and the earth" (Gen. 1:1), not empty of course, nor without all that lies between them. The earth was interspersed with water, and both were full of air, animals and plants of various kinds, whereas the heavens were full of the various lights and fires, from which the universe is formed.
Elijah, when he too had fasted forty days (I Kgs. 19:8), saw the Lord on the mountain, not in fire, as the elders of Israel had earlier (Exod. 24:9-10, Deut. 5:23), but passing beyond the fiery vision by his God-pleasing fast, he saw the Lord in the sound of a light passing breeze (I Kgs. 19:12 LXX). He had approached more closely to our Lord's words, "God is a Spirit: and they that worship him must worship him in spirit and in truth" (John 4:24). For the sound prefigured the Truth and the preaching of Him who is Truth Itself, which rang out round all the ends of the earth, and the passing breeze prefigured the Spirit and grace.
From this vision while fasting Elijah also received power to anoint a prophet in his stead and bestow upon him a double portion of the grace he possessed, and to mount up above the earth in mid-air (2 Kgs. 2:9-11). This pointed clearly towards Christ's ascension from earth to heaven which was to happen later (Acts 1:9-11). While Christ Himself was fasting in the wilderness, He defeated our tempter by force and took away his power against mankind (Matt. 4:1-11, Mark 1:13, cf. Luke 4:1-13). Having at last put down his tyranny, he set our nature free and handed him over for sport to all those willing to live according to His Gospel. In this way He fulfilled the words of the prophets and by His works inscribed grace and truth upon the symbolic events which took place in ancient times.
You see the benefits of fasting, and how it has made us worthy of so many great gifts?From Homily Six - To Encourage Fasting - Saint Gregory Palamas: The Homilies, trans. Christopher Veniamin, Mount Thabor Publishing, Waymart PA, 2009
More on fasting and the complete homily