Working for the railroad, McCoy invented a lubricating cup that automatically dripped oil. He patented it, and it was installed on locomotives. His invention greatly increased engine efficiency, and soon everyone wanted one of the "McCoy Cups." So many inferior copies were made that train engineers began to demand "the real McCoy," the genuine article.
When it comes to worship, who is the "genuine article"? If worshipers obey, they're "the real McCoy." If they don't, they aren't. Obedience is the litmus test of faith (cf. James 1:22-25).
Today in the Word, July 2003, p.36