An intense focus on "preaching of the gospel" has the power to detach us from the creative activity of God. "In vain they do worship Me," Christ says. Worship means "to hold in high regard, to venerate, to honor." Worship has become so restricted in people's minds that it is generally limited to something one does for an hour or two once a week. During that period of time, one might have a strong feeling of reverence. However, worship in the biblical sense is practical and very broad in application, involving all of the activities of every day of one's life.
Jesus castigated these people because they had made the worship of God so narrow. God was being excluded from their everyday lives by the "commandments of men" that they taught.
The worship of God involves everything we do every day. We are to honor Him, glorify Him, venerate Him in all things. Worship has very broad applications, which is why the word "commandments" is part of this context, because the commandments of God involve all of our life every day.
John W. Ritenbaugh
What Is the Work of God Now? (Part 1)
Other Forerunner Commentary entries containing Matthew 15:7: