What is the meaning of the words "Yada Lecht'cha ... "?
Rashi (in Yeshayah, 44:8): It means that Hashem made a point of knowing all their needs.
Seforno: It means that Hashem knew and put into practice that knowledge by providing them with all their needs. 1
Ramban: It refers to Hashem looking after them in the desert, where He provided them with the Manna, the quails and the roving well, and where they lacked nothing that a traveler needs.
As in Sh'mos, 2:25, 33:12 and in many other places. See Seforno.
What difference does it make whether Hashem blessed them or not?
Rashi: Since Hashem blessed them with all their needs, it would be a lack of Hakaras ha'Tov to behave like poor people who cannot afford to pay for food and drink. It is therefore correct to purchase food, in order to demonstrate their wealth.
Bearing in mind that they did not work, what is "be'Chol Ma'aseh Yadecha" referring to?
Ramban and Moshav Zekenim: It refers to the flocks and cattle 1 that they took out of Egypt and the booty from Egypt and Amalek. 2
Ramban: As in Iyov, 1:10.
Moshe mentioned only Egypt and Amalek, since this was before Yisrael defeated and took spoil from Sichon, Og and Midyan. (PF)
What are the implications of "Lo Chasarta Davar"?
Ramban: Refer to 2:7:1:2 &3.
Rashbam: It implies that whatever was unavailable, Hashem gave them free of charge, but where it is available, He gave them the means to purchase it.
Seforno: It implies that, when Edom comes to sell them food, they will realize that it is not because they (Yisrael) are short, but to benefit them because they are brothers, and in order that they should come to see the wonders of Hashem.
Hadar Zekenim: It implies that they have food and clothing, and the ability to buy if they want.
