By fasting we further prepare ourselves for God and His service.
But as for me, when they were sick, my clothing [was] sackcloth: I humbled my soul with fasting; and my prayer returned into mine own bosom. (Psalm 35:13 KJV)
And I set my face unto the Lord God, to seek by prayer and supplications, with fasting, and sackcloth, and ashes: (Daniel 9:3 KJV)
Howbeit this kind goeth not out but by prayer and fasting. (Matthew 17:21 KJV)
And he said unto them, This kind can come forth by nothing, but by prayer and fasting. (Mark 9:29 KJV)
Defraud ye not one the other, except [it be] with consent for a time, that ye may give yourselves to fasting and prayer; and come together again, that Satan tempt you not for your incontinency. (1 Corinthians 7:5 KJV)