What is Rechilus? Why does the Torah always present it together with a expression of "Halichah" (See for example, Yirmiyah, 6:28)?
Rashi: 'Rechilus' is the spreading of negative gossip that Reuven learns about Levi in Shimon's house. What generally happens is that Reuven goes from house to house, digging out scraps of derogatory information about others, which he subsequently passes on as he makes his rounds. 1
Ramban: "Rechilus" is from the same root as "Holchei Rachil 2 (with reference to peddlers, who travel from place to place to sell their wares). 3 By the same token, Holchei Rachil tend to go from place to place peddling their gossip.
Moshav Zekenim #1: [A judge] may not be Rach (soft) to this one and harsh to this one.
Moshav Zekenim #2: This is a warning against slandering people.
Moshav Zekenim #3: [A judge] may not say 'I vindicated you, but my colleagues outnumbered me [and obligated you].'
Rashi: The word 'Rachil' is equivalent to 'Ragil' - since it entails going on foot from one house to another - and a 'Chaf' and a 'Gimel' (which both sound from the same part of the mouth) are interchangeable. It seems that it was also customary for the recipient of the news to provide a snack (a sort of 'l'Chayim') to establish his guest's integrity, which explains why Targum Onkelos (and Targum Yonasan) translates "Lo Seilech Rachil" as 'Lo Seichul Kurtzin' (See also Dani'el 3:8 and Berachos, 58a). Rashi adds that the reason that Onkelos calls it 'Kurtzin' (a wink - See Mishlei, 6:13) is because they would wink and make signs to one another, so that others would not understand. Rambanrejects this. He (and the Rashbam and Moshav Zekenim) interpret 'Lo Seichul Kurtzin' as 'Do not announce Rechilus' (See Targum Yonasan, Shmuel 2. 22:14). See Ramban (DH 'Aval Ikar').
Rashi too, adds this point to his explanation of 'Rechilus'.
And he refers to it as 'Lishna Telisa'ei' (three-part talk), because it kills three people - the one who speaks it, the one who listens to it and the one about whom it is spoken (See Peirush Yonasan). Refer also to 19:16:1:1**.
But not if it is in order to bring about a'To'eles (something positive).
What is the definition of "Lo Sa'amod al Dam Re'eicha"?
Rashi: It is a prohibition against seeing a fellow-Jew dying and doing nothing about it - there where he is able to save him.
Rashbam: It means that one is obligated to save a fellow-Jew from his attacker, even if it means killing the attacker in the process.
Targum Yonasan: It means that a witness should not refrain from testifying in Beis-Din merit for his fellow-Jew.
Moshav Zekenim: If the Rebbi convicted the litigant, and a Talmid knows a reason to exempt him, he may not be silent.
Why is "Lo Sa'amod Al Dam Re'echa" taught together with Rechilus?
Riva, Moshav Zekenim: Even though I warned you against Leshon ha'Ra, if you heard that someone plans to kill Ploni, tell him!
Riva citing R"M of Kutzi: Do not tell Rechilus, for perhaps the one who hears will kill the one who spoke about him. Moshav Zekenim - this is why it does not say "v'Lo Sa'amod