Thought from Today's Old Testament Passage:
[Isaiah 58] We now commence the last division of the book, which deals with the program of peace as it sets forth the conditions, describes the ultimate realization, and insists on a principle of discrimination.
In dealing with conditions the prophet first declares the moral requirements. This message consists of a condemnation of formalism and a description of true religion. Jehovah's charge against the people is that they have observed the external ordinances of religion, and yet have complained that God has not answered them. In reply to this complaint Jehovah charges them with selfishness even in worship, and declares that their prayer is not heard, affirming that He does not accept the prostration of the body which is unaccompanied by affliction of soul.
In a passage full of beauty, true religion, with its rewards, is then described. It is expressed in rightness of action, and tenderness, which is rewarded by light, and fellowship, and answered prayer. In these external observances, such as that of the Sabbath, they must be free from all selfishness, and characterized by delight in the Lord. This is followed by true exaltation, and the realization of the promises of Jehovah.
G. Campbell Morgan, An Exposition of the Whole Bible (Westwood, NJ: Fleming H. Revell Co., 1959), pp. 317-18.