Sforno on Deuteronomy 13:9/ספורנו על דברים י״ג:ט׳

1לא תאבה לו, when he suggests that you investigate the truth of his words that a certain form of idolatry is demonstrably effective for its believers, do not assent to listen to him.

2ולא תשמע אליו, you must not listen to him to make such an experiment, and to go through a “conditional” obeisance as a test. The reason is that the moment you even entertain doubts about the utter falsity of what the seducer claims, in the end you will become a victim of his persuasiveness. You could not even entertain any doubt about G’d and His Torah unless you had never properly understood the greatness of G’d and His mastery in the universe.