Midras Keluaran 19:19: Midrash Tanchuma Buber, Mekhilta DeRabbi Yishmael, Shemot Rabbah & Bamidbar Rabbah

{R. said:} [Another interpretation:] AND YOUR HUMILITY HAS MAGNIFIED ME: R. Julianus ben Tiberinus said in the name of R. Isaac: See the humility of the Holy One. See what is written (in Exod. 19:19): MOSES SPOKE, AND GOD ANSWERED HIM OUT LOUD. Should it not rather have said, "God spoke, and Moses answered him out loud"? He did not do that. Instead, MOSES SPOKE, < AND GOD ANSWERED HIM >…. Ergo (in Ps. 18:36 = II Sam. 22:36): AND YOUR HUMILITY HAS MAGNIFIED ME.

(Exodus 19:19) "And the voice of the shofar": This is a propitious sign in Scripture. Wherever "shofar" is mentioned, this is propitious for Israel, viz. (Psalms 47:6) "G–d has risen with teruah (the shofar blast); the L–rd, with the sound of the shofar", (Isaiah 27:13) "And it shall be on that day, it shall be sounded by a great shofar, etc.", and (Zechariah 9:14) "And the L–rd G–d will blow the shofar, and will go in a tempest against Teiman (Edom)."

(Exodus 19:19) "Moses spoke and the L–rd answered him with a voice": R. Eliezer says: Whence is it derived that the Holy One Blessed be He would not speak (a new commandment) until Moses said to Him that His children had already accepted (the previous commandment)? From "Moses spoke, etc."