The first word in this week’s glorious parsha, though addressed by Moshe to the heavens, really sums up the Torah and its demands upon us. Haazinu means to listen, to pay attention, to concentrate, if you will. The Torah often emphasizes the value of listening. The entire Torah in fact is based on listening - after the commitment of naaseh, appears the equally important and vital commitment of nishma.
It is apparently not sufficient to merely do but one must also have the ability to listen and understand. The Mishna tells us that there is an echo of Sinai that may be heard every day of our lives. Many Jews do not hear that echo of holiness and purpose simply because they do not listen for it. The voice of Sinai, like the voice of Haazinu itself, is an inner voice that emanates from our souls and conscience. It instinctively tells us what is right and what is wrong, what we should do and what we should avoid doing.
But the inner voice, persistent as it may be, can easily be ignored and tuned out. If we are not willing to hear it out and truly listen to its message it eventually becomes fainter and fainter until even if we now wish to listen to it, its lack of strength prevents our hearing it. Therefore, at all costs in life, we have to concentrate on listening, on hearing the echo of Sinai within us and then acting accordingly to its bidding and advice.
Listening may often be difficult. We are innately averse to hearing criticism of ourselves and our behavior, especially if it is of the "constructive" sort. But being able to hear what others say about us, to listen carefully, even if one feels the words and accusations to be unjustified, is the mark of holiness and commitment to self-improvement.
Rabbi Yisrael Lipkin of Salant, the great founder of the mussar movement of nineteenth century Lithuania, once interpreted a verse in psalms thusly: The verse reads "that when people who seek to do me harm rise up against me, let my ears hear them." The plain and simple explanation is that when people can arise to harm me, let me have advance warning so that I can prevent their plans from actualizing.

But Rabbi Yisrael put a different twist on it. He said that when people who are my critics, who do not especially like me and vice versa, come to say things against me, give me the strength of character and fortitude to hear them out. Maybe there will be a point or two that is correct in their criticism and that therefore I can correct neglected faults and gain from the experience.
The key to self improvement is therefore clearly the ability to listen - to others and to our inner voice of Sinai as well. Moshe’s great words of the parsha to listen are spoken not only to the heavens but to us as well, in order to lift earthly beings towards a heavenly direction and way of life.