Why does it say "Lech Echol b'Simchah Lachmecha"?
Torah Temimah citing Koheles Rabah: On Erev Rosh Hashanah, Gedolei ha'Dor fast, and Hashem pardon a third of the sins [of Yisrael]. From Rosh Hashanah until Yom Kipur, individuals fast, and Hashem pardons another third. On Yom Kipur, all fast and Hashem pardons everything, and a Bas Kol comes out [after Yom Kipur] and tells them "eat your bread with Simchah
With which deeds was Hashem pleased?
Torah Temimah citing Koheles Rabah: Your Tefilah was heard.
Rashi: Your good deeds; you will merit the world to come.
Ibn Ezra: People's hearts foolishly say that these are the acts that Hashem wants (that you enjoy your food and wine).
Ibn Ezra (8), Metzudas David: If Hashem is pleased with your deeds - you did what is good and straight, then indulge and rejoice. Metzudas Tziyon - "Ki" means 'if'.
Ri Kara: If Hashem lets you enjoy what you toiled for in this world, you will know that He is pleased with your deeds - "Ki l'Adam she'Tov Lefanav Nasan Chachmah v'Da'as v'Simchah" (2:26), "Ish Asher Yiten Lo Elokim Elokim Osher u'Nechasim v'Chavod", "v'Hishlito Le'echol Mimenu v'Laseis Es Chelko Matas Elokim Hi" (6:2, 5:18).
Rid: [They say], whether you did good or evil.
R. Avigdor 1 : This refers to Avraham. After the Akeidah, Sarah asked Yitzchak where he went. He told her, and she said 'woe, woe, woe' corresponding to three Teki'us, and died. Avraham thought that the Korban was Pasul due to a Pesul in him; a Bas Kol told him "Lech
It says very close to this in Koheles Zuta and Pirkei d'R. Eliezer 32.
