Moses made a serpent of brass at the command of the Lord (Numbers 21:9).  People were saved from snake bites by looking to it.  However, in time it became a relic to worship.  In an odd way, holy things can become central to worship: A church building, prayer, fasting, the Bible, a pastor, a teacher, an institution, etc.  Means must not become ends of worship.  Nothing must be allowed to turn our eyes from the Lord, not even holy things. “Little children, keep yourselves from idols. Amen.” (1 John 5:21)

“He broke in pieces the bronze serpent that Moses had made, for until those days the people of Israel had made offerings to it.” 2 Kings 18:4 (ESV)