“Shout it aloud, do not hold back. Raise your voice like a trumpet. Declare to my people their rebellion and to the house of Jacob their sins.
For day after day they seek me out; they seem eager to know my ways, as if they were a nation that does what is right and has not forsaken the commands of its God. They ask me for just decisions and seem eager for God to come near them.
‘Why have we fasted,’ they say, ‘and you have not seen it? Why have we humbled ourselves, and you have not noticed?’ “Yet on the day of your fasting, you do as you please and exploit all your workers.
Your fasting ends in quarreling and strife, and in striking each other with wicked fists. You cannot fast as you do today and expect your voice to be heard on high.
Is this the kind of fast I have chosen, only a day for a man to humble himself? Is it only for bowing one’s head like a reed and for lying on sackcloth and ashes? Is that what you call a fast, a day acceptable to the Lord ?
“Is not this the kind of fasting I have chosen: to loose the chains of injustice and untie the cords of the yoke, to set the oppressed free and break every yoke? Is it not to share your food with the hungry and to provide the poor wanderer with shelter — when you see the naked, to clothe him, and not to turn away from your own flesh and blood?
Then your light will break forth like the dawn, and your healing will quickly appear; then your righteousness will go before you, and the glory of the Lord will be your rear guard.
Then you will call, and the Lord will answer; you will cry for help, and he will say: Here am I. “If you do away with the yoke of oppression, with the pointing finger and malicious talk, and if you spend yourselves in behalf of the hungry and satisfy the needs of the oppressed, then your light will rise in the darkness, and your night will become like the noonday.
The Lord will guide you always; he will satisfy your needs in a sun–scorched land and will strengthen your frame. You will be like a well–watered garden, like a spring whose waters never fail.
Your people will rebuild the ancient ruins and will raise up the age–old foundations; you will be called Repairer of Broken Walls, Restorer of Streets with Dwellings.
“If you keep your feet from breaking the Sabbath and from doing as you please on my holy day, if you call the Sabbath a delight and the Lord ’s holy day honorable, and if you honor it by not going your own way and not doing as you please or speaking idle words,
then you will find your joy in the Lord, and I will cause you to ride on the heights of the land and to feast on the inheritance of your father Jacob.” The mouth of the Lord has spoken. '
Isaiah 58 is a great reminder, that our fast of 1 day is not what will please the Lord. It will be our attitude, our heart and mind changing, what we do from here forward. It will be our fruit that honors the Lord and brings glory to to His name. When it is done in His name, it will last far beyond the measuring container of a single day. I think that's what God means when He says our light will then break forth like the dawn.... and He will be our rear guard.