@ByGrace - has directed everyone to the correct Scripture reference concerning fasting, but alas, no one person who posted here have understood the gist of what God has in view concerning fasting.
God is not interested in abstaining from food, to abstain from food has no spiritual value whatsoever.
God, through Isaiah, speaks of witnessing in Isaiah 58!
Note verse 6
Is not this the fast (to witness) that I have chosen? to lose the bands of wickedness (to set free the wickedness of sin)? to undo the heavy burdens (the weight of sins) and to let the oppressed (sinner) go free, and that ye break every yoke (severe bondage and affliction)?
Verse 7
Is it not to deal thy bread (Jesus) to the hungry (spiritual hunger) and that thou bring the poor (poor in spirits) that are cast out to thy house? When thou seest the naked (under judgment, sins exposed) that thou cover him (with Christ’s robe of righteousness) and that thy hide not from thyself from thy own flesh.
Verse 8 is self explanatory.
If fasting is essential in any shape or form, consider what Jesus said in Matthew 9:14-15.
14) Then came to him the disciples of John, saying, Why do we and the Pharisees fast (abstain from food) oft, but thy disciples fast not?
15) And Jesus said unto them, Can the children of the bridechamber mourn, as long as the bridegroom is with them? But the days will come, when the bridegroom shall be taken from them, and then shall they fast (witness, as per Mt 28:19).
Words in parenthesis and bold are mine.
I hope this helps.
To God Be The Glory