Fasting in the Old Testament is almost always done because of remorse for sins against God, or occasionally for wrongdoing another person. It is never done as a ritualistic event, except on the day of atonement, when the people where to afflict their souls because of their sins.
In the New Testament, the Pharisees had taken the act of fasting and turned it into a fair show of the flesh. They made it a point of pride when they fasted, not an affliction of their souls.
Not only did Christ condemn this, as far back as Isaiah, the Holy Spirit was condemning this. (To be continued.)