Vayigash (Genesis 44:18-47:27 )
“Behold! Your eyes see as do the eyes of my brother Benjamin that it is my mouth that is speaking to you” (45:12)
Rashi comments that the words, “my mouth is speaking to you” mean “in lashon hakodesh (the holy tongue.)” Purportedly, this means that Joseph offered as proof of his identity that he knew Hebrew.
But in what way was this a proof? Until now, they communicated through an interpreter, whom they assumed to be an Egyptian who obviously knew Hebrew.
Rashi's words may have an additional meaning. All matter is divided into four categories: domem (inanimate), tzomeach (vegetative), chai (living) and medaber (speaking). The last is the category of man, the only being that can speak.
But is this really so? Is man the only creature that can communicate by sound? We know that many forms of life communicate by sound. Are the sounds they make not a form of speaking? Granted, human speech is much more sophisticated, but that makes it only quantitatively distinct from animal verbalizations, but it is not a qualitative distinction. More types of sounds and a greater vocabulary are not enough to give man the distinction of being "a speaker".
The uniqueness of man is not just that he has a more sophisticated form of speech, but that he can elevate his speech to being holy. By using his speech properly, by not speaking foolishly, by avoiding defamatory speech and carrying tales, man can sanctify his speech. This is something that animals cannot do, and it is this ability to sanctify speech that merits the designation "speaker".
Although the brothers' action cannot be justified, Joseph was not totally innocent. The Torah says that “he would bring evil reports about them to his father” (Genesis 37:2) The Midrash states that all the evil reports were groundless, and Joseph was, therefore, guilty of lashon hara. During his enslavement and imprisonment, Joseph did teshuvah to purify himself of lashon hara, derogatory speech.
However, Jewish law states that an offense against another person is not forgiven until one makes proper amends and asks for forgiveness from that person. In revealing himself to his brothers, Joseph wished to tell them that he had repented for the derogatory speech he had spoken about them. “I have corrected that defective trait. I have sanctified my speech. I am now truly a medaber, a speaker,” Rashi's comment means more than that I speak Hebrew. Being polylinguistic does not yet warrant the designation of medaber. One is a "speaker" only if one's speech is kodesh, only if one sanctifies his speech.
We should indeed take pride in having the gift of speech, but unless we sanctify our speech, we are not yet unique. Avoiding the abuse of this precious gift is what makes us unique as humans.