How can one finish all one's work in six days?
Rashi: What the Torah means is that, when Shabbos arrives, you should consider it as if all your work has been completed. 1
Refer to 20:9:151:1.
So that one can refrain from thinking about one's work on Shabbos.
What is the difference between 'Avodah' and 'Melachah'?
Ramban: 'Avodah' refers to work that is not for one's immediate benefit, such as work in the fields; 1 whereas 'Melachah' refers to work from which one benefits immediately, such as preparation of food, both of which the Torah is now coming to forbid on Shabbos. 2
Having said "Sheishes Yamim Ta'avod", why does the Torah add "Ve'asisa Kol Melachtecha?
Avos de'R. Nasan chyapter 11): To teach us that if someone has courtyards or fields that lay in ruins (and there is no wotk for him him to do thyere) he should go and work on them (repair them)
See Torah Temimah, note 62.
Why does it say "six days you shall work"? Is this a Mitzvah?! And what do we include from "Kol", in this verse and in the next?
Divrei Eliyahu, Kol Eliyahu: One who is in the Midbar and does not know which day is Shabbos, every day he does only Melachah needed to stay alive (Shabbos 69b). Remember which day is Shabbos, so you can do all your Melachah in six days, i.e. also what is needed for Shabbos, and on Shabbos you will not need to do any work, i.e. even for Piku'ach Nefesh. The Torah has a hint for everything!
Rashi: Refer to 20:9:1:1.