출애굽기 20:1의 주석

וידבר אלהים AND GOD SPAKE — The word אלהים is a term for a judge. Since there are chapters in the Torah of such a character that if a person observes the commands contained therein he will receive a reward and if he never observes them at all) he will not receive punishment on their account, one might think that the Ten Commandments are also of such a character (that no punishment will follow upon the infringement of them); therefore Scripture expressly states, “God spake” — God Who is Judge, exacting punishment (Mekhilta d'Rabbi Yishmael 20:1:1).

וידבר אלוקים, after Moses had completed warning the people G’d proceeded to utter all these commandments, as we know from the testimony of Moses in Deuteronomy 5,18 את כל הדברים האלה דבר ה' אל כל קהלכם בהר, “all these words the Lord spoke to your assembled ranks from the Mountain.”

וידבר אלוקים את כל הדברים האלה, G'd spoke all these words, etc. The reason we find the attribute of Justice, i.e. אלוקים mentioned at this point is that G'd gave the Torah to the Jewish people in His capacity as the attribute of Justice as well as in His capacity as the attribute of Mercy. The words וירד אלוקים reflect the attribute of Justice, whereas the words אנכי השם reflect the attribute of Mercy. By saying אנכי ה׳ אלוקיך, G'd also revealed the mystical dimension of both attributes being part of the same essence, something we repeat twice daily when we recite the first line of קריאת שמע prayer.