Musar zu Schemot 6:9

Sometimes satisfaction and cheerfulness follow upon hearing: thus it is said (Lev. x. 20), "When Moses heard that he was content," just as anger ensues in the absence of assent and hearkening, as (Ex. xvi. 20), "Notwithstanding, they hearkened not unto Moses." ..."And Moses was wroth with them." Hatred also results from hearing, as thou must know from the case of Esau, of whom it is said (Gen. xxvii. 34), "When Esau heard," and then follows (id. xxvii. 41), "Esau hated Jacob." Mercy is known to result from "hearing"; thus God said (Ex. xxii. 26), "I will hear, for I am merciful." It is said of the righteous dead (Prov. i. 33), "Whoso hearkeneth unto me shall dwell safely." In contrast to this, it is said of the unrighteous (Job xv. 21), "A sound of fright is in his ears: in peace the despoiler shall come upon him," and so forth. Hard-heartedness results from the want of assent; thus it is said of Pharaoh in many places (Ex. ix. 12), "The Lord hardened the heart of Pharaoh and he hearkened not." A hard-hearted people is called (Deut. xxviii. 49), "A nation whose tongue thou shalt not understand, neither shalt thou hearken unto what it speaketh," and so forth.