Jamieson, Fausset and Brown on Isaiah 58:13

13. (Is 56:2; Ne 13:15-22). The Sabbath, even under the new dispensation, was to be obligatory (Is 66:23).

foot--the instrument of motion (compare Pr 4:27); men are not to travel for mere pleasure on the Sabbath (Ac 1:12). The Jews were forbidden to travel on it farther than the tabernacle or temple. If thou keep thy foot from going on thy own ways and "doing thy pleasure," &c. (Ex 20:10, 11).

my holy day--God claims it as His day; to take it for our pleasure is to rob Him of His own. This is the very way in which the Sabbath is mostly broken; it is made a day of carnal pleasure instead of spiritual "delight."

holy of the Lord--not the predicate, but the subject; "if thou call the holy (day) of Jehovah honorable"; if thou treat it as a day to be honored.

him--or else, it, the Sabbath.

not doing ... own way--answering to, "turn away thy foot from the Sabbath."

nor finding ... pleasure--answering to, "doing thy pleasure." "To keep the Sabbath in an idle manner is the sabbath of oxen and asses; to pass it in a jovial manner is the sabbath of the golden calf, when the people sat down to eat and drink, and rose again to play; to keep it in surfeiting and wantonness is the sabbath of Satan, the devil's holiday" [Bishop Andrewes].

nor speaking ... words--answering to, "call Sabbath a delight ... honorable." Man's "own words" would "call" it a "weariness"; it is the spiritual nature given from above which "calls it a delight" (Am 8:5; Mal 1:13).