What is "Ed Chinam"?
R. Yonah: It is to testify alone about an Aveirah that another did. You do not disqualify him from testimony. Your only intent is to defame him. Chazal said about this 'Tuviya sinned, and Zigud (who testified about this) is lashed 1 ?!' (Pesachim 113b). If people do not realize that Ploni is a Rasha, and they establish him to be a Tzadik, one may tell only modest, pious people. One must publicize about a Rasha, for great damage comes from honoring Resha'im. They will entice many away from the good path, and lower the honor of Tzadikim and bring close sins. There is Chilul Hashem in honoring them, for some recognize their deeds, and say that there is no lowliness in sins, and evil deeds do not lower his level. We expose Chanefim (Rashi - Resha'im who project themselves to be Tzadikim) due to Chilul Hashem (Yuma 86b). One who sins should not publicize another who sins.
Malbim: It is to testify about your colleague to obligate him for something that he did not do - this is Chinam.
R. Yonah: Even though a Talmid whom his Rebbi trusts like two witnesses, he may tell his Rebbi if he saw someone sin, this is not if a Chacham sinned. If you saw a Chacham sin at night, do not think during the day that he is a sinner. Surely he repented (Brachos 19b), for he is established to fear sin, and he worries and mourns when his Yetzer overpowers him.
What is the meaning of "va'Hapitisa bi'Sefasecha"?
Rashi: You will be enticed to your friend with your words.
R. Yonah: Hapitisa is from a root with a double letter, with two forms - Hapasis and Hapasos 1 . It is publicizing sin - making people blush and crushing the face. When you do this, you are Poseh (open) your lips and lose your Musar.
Malbim: This is if you were enticed to testify falsely for wages - you will gain Pas (bread) via your lips - or in order to repay one who did evil to you (29).
Me'iri: The verse should say Hapasosa; the Yud and Chirik are in place of a Cholem. The root is Pasas; the grammatical form is like Hasevosa.
