(32:1) Listen, heaven! I will speak! Earth! Hear the words of My mouth!
Listen heaven … Why did Moses call heaven and earth to bear witness over Israel? He said to the children of Israel: Observe heaven and earth. Although they are not rewarded for obeying God's laws, the planets and stars do not deviate from their assigned paths. You, who are rewarded when you deserve it and punished if you sin, surely you should not deviate from your assigned path (Sifrei)!
Listen, heaven … Why did Moses call heaven and earth to testify over Israel? Moses said: I am flesh and blood; tomorrow I will die. If they want to say: We never received the Torah, who shall refute them? Therefore, I call to testify over them two witnesses that will live forever (Sifrei).
(32:2) May my teaching drop like the rain, may my utterance flow like the dew; like storm winds upon vegetation and like raindrops upon blades of grass.