The 15th prohibition is that we are forbidden from leading people to idolatry by speaking to them and encouraging them to serve an idol — even if the person himself did not serve the idol or do anything other than leading [others] to it. If he misleads the many people1 he is called a madi'ach.

The source of this prohibition is G‑d's statement (exalted be He),2 "Wicked men among you have lead the city's inhabitants astray saying ['Let us go and serve false gods.']" If he leads an individual person astray, then he is termed a meisis,3 the source being G‑d's statement (exalted be He),4 "If your maternal brother tries to lead you astray […secretly, saying, 'Let us go and serve false gods…']."

But in this prohibition we are speaking exclusively about a madi'ach, and the source of this commandment is G‑d's statement (exalted be He),5 "[You may not mention the name of a false gods;]You must not let it be heard through your mouth."

Our Sages said in tractate Sanhedrin,6 "The verse, 'You must not let it be heard through your mouth,' is the prohibition of meisis.7 [The Talmud then challenges,] But the prohibition of meisis is already written explicitly: '[If your maternal brother tries to lead you astray…secretly, saying, 'Let us go and serve false gods…You shall put him to death…] and they will no longer do [this wicked act in your midst]'! Rather, the verse ['You must not let it be heard through your mouth'] is the prohibition of madi'ach." The Mechilta of Rabbi Yishmael similarly says, "The verse, 'You must not let it be heard through your mouth,' is the prohibition of madi'ach."

One who transgresses this prohibition is punished to death by stoning. In the words of tractate Sanhedrin,8 "Those who lead a city to idolatry9 are punished by stoning.

The details of this mitzvah have been explained in the tenth chapter of Sanhedrin.10