וַיֹּ֣אמֶר לָהֶ֗ם כֹּֽה־אָמַ֤ר יְהוָה֙ אֱלֹהֵ֣י יִשְׂרָאֵ֔ל שִׂ֥ימוּ אִישׁ־חַרְבּ֖וֹ עַל־יְרֵכ֑וֹ עִבְר֨וּ וָשׁ֜וּבוּ מִשַּׁ֤עַר לָשַׁ֙עַר֙ בַּֽמַּחֲנֶ֔ה וְהִרְג֧וּ אִֽישׁ־אֶת־אָחִ֛יו וְאִ֥ישׁ אֶת־רֵעֵ֖הוּ וְאִ֥ישׁ אֶת־קְרֹבֽוֹ׃
און ער האָט צו זײ געזאָגט: אַזױ האָט געזאָגט ה׳ דער גאָט פֿון ישׂראל: טוט אָן איטלעכער זײַן שװערד אױף זײַן דיך, גײט דורך הין און צוריק פֿון טױער צו טױער אין לאַגער, און הרגעט איטלעכער זײַן ברודער, און איטלעכער זײַן חבֿר, און איטלעכער זײַן קרוב.
Rashi
כה אמר הי וגו׳ THUS SAITH THE LORD etc. — Where did he say so? In the command, (Exodus 22:19) “He that sacrificeth unto any god shall utterly be destroyed”. Thus is it stated in the Mechilta.
Chizkuni
כה אמר, “thus has said the Lord, etc.;” where is G-d recorded as having said this? In Exodus 22,19: זובח לאלוהים יחרם, “whoever sacrifices to a god shall be proscribed.”
Ramban
THUS SAITH THE ETERNAL, THE G-D OF ISRAEL. The reason for this expression383‘Elokei’ (the G-d of) Israel — the Divine Name which denotes the attribute of justice. is that since the worshippers of the calf had intended to sacrifice to the G-d of Israel, therefore the attribute of justice extracted punishment from them, because they “mutilated the shoots” [of faith],384See Note 308 above. and besides, for the judgment is G-d’s.385Deuteronomy 1:17. It is for this reason that he [Moses], said of the Levites, for the G-d of Israel hath separated you from the congregation of Israel,386Numbers 16:9. for the Service is to the G-d of Israel, and to His Name they were separated by virtue of this meritorious deed.