The context gives no indication that the Israelites were not observing the Sabbath on the seventh day. Rather, their attitude and way they were observing it contrasted with God's desire. Carnally, man feels free to worship God as he good and well pleases. These attitudes, as well as the practices, break the second commandment.
This passage parallels Amos 5:21-27, which was preached about the same time as Isaiah 1:13-15. Both show crowds in a festive attitude, yet God rejects their "worship" as worthless. Their "holiness" was a sham because it was not backed by righteous conduct in their daily lives. The spirit behind their worship was wrong. Their futile sacrifices indicate their hypocrisies: These people had the morals of alley cats; eyes hot with lust and greed; and fortunes built on crime, envy, murder, and deceit. In reality, they were stingy, hateful gossipers who on the Sabbath appeared before God as if everything was okay.
What kind of a god would accept the conduct that the Israelites exhibited? Certainly not the true God! They were going through the motions of punctilious observance, but their hearts were elsewhere, as their daily conduct showed. God is more concerned about right relationships between people than an overly scrupulous regard for formal worship on the Sabbath. Worship cannot be separated from the character and attitudes displayed in daily life. It is a person's reaction to God all through the week, not just on the Sabbath, that matters. We cannot mock God and somehow believe that we will get away with it.
In Isaiah 2:5-18, God testifies of a culture immersed in all sorts of idolatry. He sees a people enslaved by the superstition of astrology—they do not seek God's judgment, but they will seek and do what the omens read! Their material success has produced a self-confidence that deceives them into believing that God is unnecessary. This chapter reveals what resides at the foundation of much idolatry—pride, as expressed in the phrases, "The lofty looks of man" and the "haughtiness of men." Pride drives mankind to resist God, so they will not submit to the way He wants our response—our worship—done.