The singular Dibros and the eternal tzaddik

איתא במדרש וברש"י הביאו מ"ש אנכי ה' אלקיך בלשון יחיד ליתן פתחון פה למרע"ה כו'.

It is brought in the Midrash, and Rashi cites it, that "I am Hashem your God" was said in the singular in order to give Moshe Rabbeinu an opening to plead, etc.

The Sefas Emes begins from the Midrash (cited by Rashi) that the Aseres Hadibros open in the singular ("Elokecha," your God) so that Moshe would later have "an opening of the mouth" to defend Bnei Yisrael after the cheit ha'egel — arguing that the command had been addressed to him individually.

פי' הענין כמ"ש צדיק יסוד עולם כאשר ראינו שמשה רבינו ע"ה בכחו תיקן כל בנ"י ולעולם יש בישראל צדיק אחד עכ"פ אשר בכחו לקבל הדברות.

The explanation of the matter is as it is written, "a tzaddik is the foundation of the world" — as we saw that Moshe Rabbeinu, peace be upon him, by his power rectified all of Bnei Yisrael; and there is always at least one tzaddik in Yisrael who has the power to receive the Dibros.

The singular form points to a deeper truth: a single tzaddik can be the "foundation of the world" (Mishlei 10:25). Just as Moshe's spiritual power rectified all of Bnei Yisrael, so in every generation there exists at least one tzaddik with the capacity to receive the Divine word.

כי הנה אנכי ה' אלקיך הוא לשון גזירה כמו יהי רקיע ואינו מצוה בלבד.

For behold, "I am Hashem your God" is a "decree-language," like "let there be a firmament," and is not merely a command.

"Anochi Hashem Elokecha" is not only a mitzvah to be obeyed but a creative decree — like the utterances of creation ("let there be") — that establishes an enduring reality.

א"כ לעולם אין לזה ביטול לכן יש תמיד צדיקים מיוחדים בתוך בני ישראל:

If so, this can never be nullified; therefore there are always special tzaddikim within Bnei Yisrael.

Since it is a creative decree, it can never be voided — and so, as a permanent reality, there will always be unique tzaddikim among Bnei Yisrael capable of receiving and embodying the Torah.

Summary: The Aseres Hadibros open in the singular both to give Moshe an opening to defend Bnei Yisrael and to teach that "Anochi Hashem Elokecha" is a creative decree, not merely a command. Because such a decree can never be nullified, there is always at least one special tzaddik in every generation — a "foundation of the world" — with the power to receive the Divine word.