The giving of the Torah represents a fundamental transformation in the cosmic order: Akeidat Yitzchak 44 teaches that when God wished to give the Torah to Israel, He declared that henceforth the lower realms would ascend to the upper, and the upper would descend to the lower — God Himself descending first, as written in the verse describing His descent upon Har Sinai, followed by Moses ascending.
Akeidat Yitzchak 31 adds that the fulfillment and perfection of creation was reached at matan Torah, from which point forward the existence of the natural order was suspended and made wholly dependent on the observance or neglect of the Torah's commandments.
The event at Sinai was extraordinary in every dimension — the greatness of the Teacher, the awesome and publicized nature of the assembly, and the vast number of those who heard, numbering well over six hundred thousand men besides women and children — as Akeidat Yitzchak 45 describes.
Akeidat Yitzchak 89 further elaborates that all of Israel heard the Ten Commandments from God directly, and that the first two — "Anochi" and "Lo yihyeh lecha" — were heard from the Divine Presence itself, while the remaining 611 commandments were transmitted through Moses.