Theoretically, when a person’s intellect and the root of his soul are sufficiently lofty—as was the case with Abraham and Moses—he requires no holy sanctuary, for he himself is the sanctuary.
Thus, Moses did not need to enter the Holy of Holies, for he himself had a holiness of a higher kind than that of the Temple.
(That is why Moses’ personal tent, where he sat and meditated, was given the same name as the sanctuary—the “tent of meeting.”)
—Rabbi Adin Steinsaltz