לֹ֣א תִשְׁמַ֗ע אֶל־דִּבְרֵי֙ הַנָּבִ֣יא הַה֔וּא א֛וֹ אֶל־חוֹלֵ֥ם הַחֲל֖וֹם הַה֑וּא כִּ֣י מְנַסֶּ֞ה יְהוָ֤ה אֱלֹֽהֵיכֶם֙ אֶתְכֶ֔ם לָדַ֗עַת הֲיִשְׁכֶ֤ם אֹֽהֲבִים֙ אֶת־יְהוָ֣ה אֱלֹהֵיכֶ֔ם בְּכָל־לְבַבְכֶ֖ם וּבְכָל־נַפְשְׁכֶֽם׃
Nie usłuchasz słów proroka takiego, albo snowidza takiego, gdyż doświadcza was Wiekuisty, Bóg wasz, aby poznał, czy miłujecie Wiekuistego, Boga waszego, całem sercem waszém i całą duszą waszą.
Rashi
או מופת OR A WONDER showing itself on the earth. — Nevertheless you shall not hearken unto him (although the sign or the wonder come to pass; cf. v. 3). But if you ask, why then does God give him the power to perform a sign? Scripture replies, (v. 4) “for the Lord your God trieth you, [to know whether you really love the Lord your God]” (Sifrei Devarim 84:1; cf. Sanhedrin 90a).
Rashbam
אלה אלוהיך ישראל אשר העלוך, were the Israelites all idiots that they would accept such a statement? Had they not all experienced the miracles performed by the G’d of Israel only less than 3 months ago?The declaration is to be understood as based on the premise subscribed to by most idolaters that while it is true that there is a G’d in heaven Who had created the universe, the teraphim were held to possess divine powers, exercising same just as did the prophets who performed miracles. The former were agents of spiritually negative forces, known in our parlance as רוח הטומאה, the prophets performed their miracles by invoking the spiritually positive forces, G’d in heaven. The people who had made the golden calf, or who had seen it emerge from the mould, proclaimed that the same force which had produced the golden calf had also been instrumental in freeing the Jewish people from the enslavement by the Egyptians. They implied that such teraphim may sometimes be the embodiment of holy spirit, other times of Satan’s spirit. They insisted that seeing that the calf had materialised at the time when the Jewish people were in need of a replacement for Moses, this was proof that it was a replacement for Moses, and if they would now carry the golden calf in front of them, or have it walk in front of them, this would be equivalent having the holy spirit walking ahead of them. [I fleshed out the author’s words. Ed.] We know that Lavan (Genesis 31,30) accused Yaakov of having stolen his “gods” which was the description he gave to his “teraphim.” He himself had admitted that Yaakov’s G’d had enriched him, and yet for himself he paid heed to these teraphim. If G’d allowed the spiritually negative forces to appear as possessing divine powers, He did so in order to test the loyalty of the Jewish people who had been warned not to have any truck with witchcraft or those who practiced this art. Moses spells all this out in Deuteronomy 13,4. The prohibition against אוב, ידעוני, and a variety of different demonic and other sorcery performing spirits has been repeated in the Torah several times. Loyalty of the people to their G’d can be proven only when alternative sources of what one desires are offered or appear as being offered.
Rambam Introduction to the Mishnah
And it is not for us to examine the one who [claims] prophecy and we do not request a sign. And even – if to establish his prophecy – he does from the signs and wonders, the grandeur of which have not known, he is to be strangulated. And we do not examine his signs, as the reason for the existence of these signs is that which the verse states (Deuteronomy 13:4), "for the Lord, your God, is testing you."