The Torah commands in (Exodus 23:13): "And the name of other gods you shall not mention." The Mekhilta expands this prohibition far beyond what a casual reading might suggest. It is not just about prayer or worship. It reaches into the most mundane aspects of daily interaction with non-Jewish neighbors.
The first application: you shall not swear to a gentile by his god. Even in a business context, even to seal a deal or confirm a promise, invoking the name of a foreign deity is forbidden. The prohibition does not depend on whether you believe in that god. The mere act of speaking the name in an oath gives it a status it does not deserve.
But the Mekhilta goes further. "Do not make a meeting house for him" — do not arrange to meet someone at a place of idol worship. "Do not determine where he lives by reference to idolatry" — do not give directions using a pagan temple as a landmark, saying something like "he lives near the temple of such-and-such." And "do not arrange to meet him by a certain idol" — do not set an appointment using an idol as the meeting point.
These rulings reveal how seriously the rabbis took the contaminating potential of idolatrous language. Mentioning the name of a foreign god — even in passing, even as a geographic reference — normalizes its presence in your speech and your mental landscape. Every casual mention chips away at the exclusivity of devotion to God.
The Mekhilta's reading transforms "you shall not mention" from a narrow ritual prohibition into a comprehensive discipline of speech, directing Jews to scrub their daily language of any reference that might grant legitimacy to foreign worship.