The Zohar, Chapter “Lech Lecha (Go Forth),” Item 315: “Bless the Lord, you His angels… upon hearing the voice of His word.”
A person is called an angel when he performs actions automatically, without using his mind. He doesn’t have his own head (Rosh) and does what he is told. He carries out what someone else thinks. This state is called “angel” since an angel is a force that acts without any discernment.
Hence, in the instruction of “we shall do and we shall hear,” we carry out “we shall do” as angels. This is why it is written: “…His angels…upon hearing the voice of His word.” We too shall act and then we shall hear. Acting without inner agreement or a clear understanding of the reason and purpose of our deed (since they are the attributes of a higher state), we merit a higher degree.
As a matter of fact, this is the most natural way to act. It is similar to a child who while playing an unfamiliar game repeats the words of a grown-up even though he does not understand the meaning. We can say any nonsense, and the child will repeat it seriously. If we perform an action, he will copy it with total willingness and passion. This is how a child learns. A “small one” doesn’t possess a mind (Rosh, the head of the Partzuf); a mind is the attribute of a “big one.” A “small one” has only a body (Guf of the Partzuf) to carry out the tasks.
However, when the lower one follows the Upper One and annuls himself before him, then he acquires the mind of the Upper One and becomes similar to him. This is the essence of “we shall do, and we shall hear.”
From the 2nd part of the Daily Kabbalah Lesson 8/3/10, The Zohar