Zohar 2:93b-94a

Jewish Mysticism
The ten words of the Torah [i.e., the Decalogue] contain all the [613] commandments, comprehending what is above and below, the principle of the ten words of creation … These [ten words] were carved on the tablets of stone, and all that was hidden in them was visible to their [the Israelites’] eyes, for they all knew and considered the secret of the 613 commandments of the Torah contained in them. All was visible to them, all was understood in the minds of Israel and all was revealed to their eyes. In that time all the secrets of Torah, above and below, were not removed from them, for they saw with their eyes the splendor of the glory of their Master. Since the day when God created the world there was nothing like His revealing His glory on Sinai.

Translated by Elliot Wolfson in Through a Speculum that Shines- Vision and Imagination in Medieval Jewish Mysticism, Princeton- Princeton University Press, 1994.