What are the implications of "Vesamu es Sh'mi"?
Rashi (citing the Sifri) and Ramban: It implies that the Kohanim should bless Yisrael with the Shem ha'Meforash 1 ("Sh'mi", 'he'Meyuchad Li'!). 2
Moshav Zekeinim (citing the Yerushalmi Gitin, 5:9): One should not say 'A Kohen who transgresses Arayos and murder 3 is blessing me', because it is I (Hashem) who blesses you, and not him!'
Sotah, 38a: See answer #1 and note. To teach us via a Gezeirah Shavah "Vesamu" "Lasum es Sh'mo Sham" - Re'ei Devarim, 12:5, that the obligation to bless Yisrael with the Shem ha'Meforash, is confined to the Beis-Hamikdash but outside the Beis-Hamikdash, 4 the Kohanim are permitted to bless Yisrael with a Kinuy.
Refer to 6:27:151:1-2.
Moshav Zekeinim (citing R. Simchah): Even though a Kohen who murdered may not Duchen (B'rachos 32b), if he repented, he may. See also Torah Temimah, note 159.
Ramban (in Pasuk 23): The command there was in connection with the setting-up of the Mishkan, "where Hashem has commanded the B'rachah of life forever" (Tehilim, 133:3); There, the blessing was said with the full Name of Hashem, elsewhere, it is with one of Hashem's Kinuyim (Secondary Names); There it was said as one B'rachah; elsewhere, as three - 'Yevarch'cha, Ya'er, Yisa' (See R. Chavel's footnotes).
What are the implications of "va'Ani Avorachem"?
Rashi #1, Targum Onkelos and Targum Yonasan: It implies that Hashem will bless Yisrael (by agreeing with the Kohanims' blessing - Rashi). 1
Rashi #2: It implies that (when the Kohanim bless Yisrael) Hashem will bless the Kohanim. 2
Sotah, 38b: It implies that Hashem waits in anticipation for the Kohanim to bless Yisrael.
Megilah, 18a: Based on the fact that the Torah writes "va'Ani Avorachem", and the B'rachah of Hashem is 'Shalom' - as the Pasuk states in Tehilim, 29:11, the Chachamim instituted the B'rachah of 'Sim Shalom' after Birchas Kohanim. 3
Sifri: Yisrael should not claim that their B'rachos are dependent upon the whim of the Kohanim, and the Kohanim should not claim that they are the ones who bless Yisrael - because the Torah writes "va'Ani Avorchem!" 4
QUESTIONS ON RASHI
Rashi writes that the Kohanim bless with the Shem ha'Mefurash. Which Name is that?
Sotah 38a: It refers to Hashem's name 'Havayah', pronounced like it is written (Rashi). 1 Outside the Beis-Hamikdash, the Kohanim use a Kinuy 2 (Alef-Daled).
R. Bachaye and the Gevuras Ari (on Yoma, 66a, citing Rav Hai Gaon): It is Hashem's twelve-letter name, which contains the Name Havayah three times, each time with a different punctuation.
Tosfos Yom Tov (Yoma 6:2, citing the R'MaK) - people fell on their faces only when the Kohen Gadol said the Shem ha'Mefurash in the Avodah of Yom Kipur. Perhaps at all other times it was said with the punctuation of the Name 'Alef-Dalet-Nun-Yud'.
Kol Eliyahu: The former is called "Sh'mi"; whereas the Kinuy is a mere Zeicher of His name. "Ve'samu es Sh'mi" teaches Birkas Kohanim in the Mikdash. The Sifri however, includes outside the Mikdash from "be'Chol Makom asher Azkir es Sh'mi" - in Yisro Sh'mos, 20:21.
