'Fast' in the Bible

Blessed is the man that doeth this, and the son of man that holdeth fast to it; that keepeth the sabbath from profaning it, and keepeth his hand from doing any evil.

for thus saith Jehovah: Unto the eunuchs that keep my sabbaths, and choose the things that please me, and hold fast to my covenant,

Also the sons of the alien, that join themselves to Jehovah, to minister unto him and to love the name of Jehovah, to be his servants, every one that keepeth the sabbath from profaning it, and holdeth fast to my covenant;

Wherefore have we fasted, and thou seest not; have afflicted our soul, and thou takest no knowledge? Behold, in the day of your fast ye find what pleaseth you, and exact all your labours.

Behold, ye have fasted for strife and debate, and to smite with the fist of wickedness; ye do not at present fast, to cause your voice to be heard on high.

Is such the fast that I have chosen, a day for a man to afflict his soul, that he should bow down his head as a bulrush, and spread sackcloth and ashes under him? Wilt thou call this a fast, and a day acceptable to Jehovah?

Is not this the fast which I have chosen: to loose the bands of wickedness, to undo the thongs of the yoke, and to send forth free the crushed, and that ye break every yoke?