Likutei Moharan 22:18/ליקוטי מוהר"ן כ״ב:י״ח

118. The concept of “we will do and we will hear” applies in each and every world. Likewise, in the [world of] angels there is “we will do and we will hear.” As is written (Psalms 103:20), “Strong warriors who do His word, so as to hear the sound of His word.” And as our Sages said (Shabbat 88a): “[When the Jewish people preceded ‘we will hear’ with ‘we will do,’ a heavenly voice rang out:] ‘This secret which the ministering angels employ, who revealed it to My children?’ As is said, ‘Strong warriors….’”