"Listen heaven! I will speak! Earth! Hear the words of my mouth!"
Why is it that heaven should “listen” while the the earth should “hear?” Arizal asks fourteen more such questions about word usage before he begins his answer.
In the Torah there are revealed and hidden parts, that is, simple meaning and secrets, and the secret is not for everybody, but only for people who are themselves like angels. The simple meaning, however, is for common people. It is about this secret meaning that the angels objected when God wanted to give the Torah to Israel. They said, “What greatness will it be for Your Name?” - that is, for the Torah, which is all the names of God - “Why are its secrets given to men on earth?”
The paradox that the angels did not comprehend was that since the simple meaning of the Torah was not fitting for them, since they are not mortal, the Torah had to be given to men, to whom the simple meaning applies, and the secrets were given with it.
This is the meaning of “Listen, heaven!” Moses is talking to those special righteous people who, while on earth, are similar to angels in heaven. “Listen” implies that these things are not said out loud, but from mouth to ear. And “I will speak,” (“Adabeira,”) implies things which are hard to understand. In contrast, the simple meaning can be heard by common people, that is why they can “hear the words.” To the secrets, however, the following principles apply: "not every brain can sustain them," and "not everyone who wants to occupy himself with the names of God should do so".
Art: Karl Witkowski - Secrets