"Do not worship them"—Exodus 20:5.
We are forbidden to worship an idol employing any practice unique to that idol. For example, in ancient times there was an idol called Markulis. Its worship called for casting a rock in its direction. Throwing a rock at Markulis would be a violation of this prohibition—while throwing a rock at any other idol would not.
(This is in addition to specific modes of idol worship that are forbidden whether or not they are part of the protocol prescribed for that deity. See Negative Mitzvah 5 for more on this topic.)
