To those who remove the yoke and cease from the pointing of the finger and the speaking of wickedness, Jehovah says, "Then your light will rise in the darkness,/And your gloom will be like midday;/And Jehovah will guide you continually, / And satisfy your soul in the dry times,/And strengthen your bones;/And you will be like a watered garden,/And like a spring of water,/Whose waters do not deceive./And those who are of you will rebuild the ancient ruins;/You will raise up the foundations of generation upon generation;/And you will be called the repairer of the breach,/The restorer of the paths in which to dwell" (vv. 10b-12). These verses indicate that the one who fasts in the right way will be full of light and life, that he will be useful, and that he will enable others to go on.
In verse 13 Jehovah instructs the house of Jacob to turn back their foot from the Sabbath, from doing what they please on His holy day. They were to call the Sabbath a delight and honor it, not doing their own ways, nor finding their own pleasure and speaking idle words. They were to keep the Sabbath by enjoying God, having been fired and replaced by Him. But if they did not keep the Sabbath in this way, they would be those who do their own ways, find their own pleasure, and speak idle words.
If they honor the Sabbath, they will have delight in Jehovah, and He will cause them to ride upon the heights of the earth, and He will feed them with the inheritance of Jacob their father (v. 14).
In the book of Isaiah, we have seen that God has an economy. In His economy God makes Christ the centrality and universality. God wants us to learn one lesson—to stop our doing and to keep away from the taste of anything other than Christ. We should be replaced by Christ and enjoy God continually. This is the purpose for which Christ died for us and was resurrected for us. He is our Sabbath and our food. Now we can rest in Him, feed on Him, and have Him as our replacement in every way and in everything.