신명기 13:9의 Halakhah

That He prohibited an incited one from arguing the merit of the inciter. Even if he [knows of] a merit for him, it is not permitted for him to mention it and argue [it]. And that is His, may He be blessed, saying, "nor have compassion on him" (Deuteronomy 13:9). And it appears in the explanation (Sifrei Devarim 89:4), "[It means,] do not argue in his merit." (See Parashat Re'eh; Mishneh Torah, Foreign Worship and Customs of the Nations 5.)

That He prohibited an incited one from being silent about something incriminating that he knows about the inciter that will bring about the punishment upon him. And that is His, may He be exalted, saying, "and you may not shield him" (Deuteronomy 13:9). And it appears in the explanation (Sifrei Devarim 89:4), "'And you may not shield him' - if you know something incriminating about him, you are not allowed to remain silent." (See Parashat Re'eh; Mishneh Torah, Foreign Worship and Customs of the Nations 5.)

To not love the seducer: That we have likewise been prevented from bending our ear to the words of a seducer and that we not endear him in any manner. And the content of a seducer is one who seduces one Israelite to worship idolatry, such as one who praises the actions of idolatry to him; and he praises it in order that he will follow it and serve it and leave from under the wings of the Divine Providence. And about this is it stated (Deuteronomy 13:9), "You shall not long for him."