וְהַנָּבִ֣יא הַה֡וּא א֣וֹ חֹלֵם֩ הַחֲל֨וֹם הַה֜וּא יוּמָ֗ת כִּ֣י דִבֶּר־סָ֠רָה עַל־יְהוָ֨ה אֱלֹֽהֵיכֶ֜ם הַמּוֹצִ֥יא אֶתְכֶ֣ם ׀ מֵאֶ֣רֶץ מִצְרַ֗יִם וְהַפֹּֽדְךָ֙ מִבֵּ֣ית עֲבָדִ֔ים לְהַדִּֽיחֲךָ֙ מִן־הַדֶּ֔רֶךְ אֲשֶׁ֧ר צִוְּךָ֛ יְהוָ֥ה אֱלֹהֶ֖יךָ לָלֶ֣כֶת בָּ֑הּ וּבִֽעַרְתָּ֥ הָרָ֖ע מִקִּרְבֶּֽךָ׃
Prorok zaś ów, albo snowidz ów, uśmiercony będzie, gdyż głosił odstępstwo od Wiekuistego, Boga waszego, który wywiódł was z ziemi Micraim, i wyzwolił cię z domu niewoli, - aby zwieść cię z drogi, o której przykazał ci Wiekuisty, abyś postępował nią: a wytępisz to zło z pośród siebie.
Rashi
סרה [BECAUSE HE HATH SPOKEN] סרה — i.e. something that is strange in the world (more lit., removed from the world), something which never existed and was never created (a pure invention), and which I never bade him say; detournure in O. F.
Chizkuni
כי דבר סרה, “for something perverse;” he falsified the message he claimed to have received from Me,” What he did was to lead you astray from revering Me. Where is the warning to such a false prophet not to practice his perversion given? It has been spelled out in the words of the Torah, with which he his familiar, “do not listen to him!” (Exodus 23,13) (Compare Torah sh’leymah by Rabbi Menachem Kasher item 182 on that verse.)
Ibn Ezra
he spoke rebellious i.e., he spoke rebellious words. Compare, “in the multitude of counsellors, [counsel] is established” [Proverbs 15: 22].