(לג) וַיְכַ֥ל מֹשֶׁ֖ה אֶת־הַמְּלָאכָֽה׃ {פ} (לד) וַיְכַ֥ס הֶעָנָ֖ן אֶת־אֹ֣הֶל מוֹעֵ֑ד וּכְב֣וֹד ה' מָלֵ֖א אֶת־הַמִּשְׁכָּֽן׃ (לה) וְלֹא־יָכֹ֣ל מֹשֶׁ֗ה לָבוֹא֙ אֶל־אֹ֣הֶל מוֹעֵ֔ד כִּֽי־שָׁכַ֥ן עָלָ֖יו הֶעָנָ֑ן וּכְב֣וֹד ה' מָלֵ֖א אֶת־הַמִּשְׁכָּֽן׃
(33) ...When Moses had finished the work, (34) the cloud covered the Tent of Meeting, and the Presence of ה' filled the Tabernacle. (35) Moses could not enter the Tent of Meeting, because the cloud had settled upon it and the Presence of ה' filled the Tabernacle.
Four theories:
ולא יכל משה לבא אל אהל מועד "AND MOSES WAS NOT ABLE TO COME INTO THE TENT OF MEETING"
But another verse says, “And when Moses would into the Tent of Meeting..." (Numbers 7:89) There is, however, a third verse that reconciles these apparently contradictory verses, for it says here, “Because the cloud had settled upon it.” Hence I deduce: so long as the cloud was upon it “he was not able to come into the appointed tent,” but as soon as the cloud disappeared he entered it and spoke with God.
And the Presence of God filled the mishkan. This is one of many verses where the order of words are reversed. It is for the honor of Heaven the words were reversed. For if it had said "And the mishkan was filled with the Presence," it would mean that the presence were contained within the mishkan which held it. Now, where it is written "And the Presence of God filled the mishkan," it means that the Presence is great and the mishkan is contained in its midst.
Torah also says "And God called to Moshe from the tent of meeting" (Leviticus 1:1) - every place where the cloud is, Moshe was unable to enter without being called, for then he was given permission to enter. And so too it says at the giving of the Torah, "And Mount Sinai was all in smoke" (Exodus 19:18), and it is written after it "And God called Moshe to the top of the mountain, and Moshe ascended" (Exodus 19:20). Our rabbis explained: for each word, there was [first] a "calling" [to Moshe] - for this is the way of the world: to call a person when one wants to speak with them, that they should know that one is speaking to them.
trans. Rabbi David Kasher, ParshaNut pp.134-135
Know that before creatures were created, there was a simple supernal light that filled all existence; and there was no empty space, like a vacuum, but all of existence was filled with a simple, infinite light. It had no aspect of beginning or end; rather all was one simple light equally distributed, and this was called the light of Ayn Sof, The Infinite One. Then, when it arose in God's simple will to create worlds, to bring to light the completion of acts, names, and designations, the Ayn Sof then concentrated Itself in the central point, and there in the actual center of that light, God concentrated the light and removed it on all sides from around the central point. Then there was an empty space, a complete vacuum, from that actual central point. Now, this contraction (tzimtzum) was equal all around that central, empty point, in such a manner that that empty space was a circle completely equidistant all around. Now, after this contraction, there remained a completely empty vacuum in the middle of the actual light of the Ayn Sof, and there was now a space in which the things to be created, formed, and made could exist.