Ha'azinu: Chapter 2
"Give ear, O heavens - hear heavens"

Rabbi Chiya tells us about the time that Isaiah said, "Hear, heavens, and give ear, earth"; when Isaiah was then challenged by a voice he answered that it was not he himself who was speaking. And yet when Moses spoke it was indeed his own voice. Rabbi Yosi's interpretation is that Moses was addressing the supernal heaven and earth while Isaiah was addressing the lower heavens and earth.