Babylonian Talmud Shabbat 88b
R. Joshua ben Levi said: With each and every word that issued from the mouth of the Holy One, the entire world, all of it, was filled with the fragrance of spices.
But if the first word filled the world, where did the fragrance of the second word go? Out of His treasuries the Holy One brought forth a wind, which carried each fragrance along in orderly succession.
כי קאי רבי בהא מסכתא לא תשייליה במסכתא אחריתי דילמא לאו אדעתיה
When Rabbi is in one tractate, do not ask him regarding a different tractate.
Pahad Yitzhak, Shavuot, Essay #9, Rabbi Yitzhak Hutner (translation by Rabbi Abe Friedman)
And we find, according to this, that in the truth of the matter at the moment when one Statement held dominion, the world had no open space for the content of any other Statement, and a special action of removing the first Statement's dominion was necessary in order to clear space for its fellow. "Each one passing one by one."
And the same structure and characteristic holds true in the spiritual world of a person who gives himself over to the words of Torah. At the moment when one Statement of words of Torah has dominion over his soul, every space in his soul is perfumed by it. And only through a special action of disconnection and passing is it possible for a second Statement to be grasped in his soul.