Fast and Sabbath
This is the fast that I have chosen: to loose the bonds of wickedness, to cut off the bands of treachery, to let the oppressed go free, and to break every yoke; To share your bread with the hungry, and to bring the stranger to your house; when you see the naked, to cover him; and to refuse not one of your own flesh. (Is: 58:6-7)
These things that we are to do are symbolic not just literal. In the most general sense, to fast is do deny ones own desires of the flesh. To loose the bonds, cut off bands, break every yoke refers to helping others to break free of whatever false ideas imprison them. To share bread, bring in the stranger, and cover him, all speaks to giving the knowledge we have gained to others for spiritual food, shelter and clothing. For these things, the Lord has given His promise:
Then shall your light break forth as the morning and your righteousness shall spring forth speedily; and your righteousness shall go before you; the glory of the Lord shall be your reward. (Is 58:8)
And the Lord shall guide you continually and satisfy your soul with rich food; and strengthen your bones; and you shall be like a watered garden, and like a spring whose water fails not. And some of you shall build the old waste places; you shall raise up the foundations of many generations; and you shall be called the repairer of the breaches, the restorer of paths to dwell in. (Is 58:11-12)
Thus says the Lord: Keep judgement, and do justice; for my salvation will come soon and my righteousness will be revealed. Blessed is the man who does this, and the son of man who lays hold on it; he who also keeps the sabbath that he may not profane it, and guards his hands from doing any evil. (IS 56:1-2)
If you turn away your foot from the sabbath, from doing your pleasures on my holy day; and call the sabbath a delight, the holy of the Lord, honorable; and shall honor it, not doing on it your own ways, nor doing on it your own pleasure, nor speaking idle words; Then you shall put your trust in the Lord; and I will cause you to ride upon the high places of the earth and feed you with the heritage of Jacob your father; for the mouth of the Lord has spoken it. (IS 58: 13-14)
This is the meaning I was given to understand: The sabbath here should be seen not just as a day of the week, but in a spiritual sense. The sabbath represents a day of rest. This means that in the Lord's day, we do nothing of our own pleasure or desire, but only His. We cease from labor, which means to not do things by our own will power. When we do this, we put our trust in the Lord and receive His promises.
All together, these things we should do are done not by our will but by "resting" and allowing Him to work through us, in faith and trust of Him. Thus, His glory is our reward.