What is the significance of eating to satiation?
Radak: He did wondrously with you - in one year, he paid the grain of four years. According to Chazal (that the grain grew in 11 days), it was even more wondrous.
Malbim: Aside from paying them to increase grain until He completes what He made them lose in the years of hunger, He will send a Brachah in the innards - he eats a little, and it is blessed in his innards.
What do we learn from "[Achol v'Savo'a] v'Hilaltem Es Shem Hashem Elokeichem"?
Malbim #1: He eats a little, and it is blessed in his innards. This is a supernatural miracle - for this, "v'Hilaltem Es Shem Hashem Elokeichem" who put His Hashgachah on you to do this wonder. This increases the honor of His great name.
Malbim #2: This also hints to the law that if [the Tzibur] began to fast [due to lack of rain] and rain descended, they do not complete the fast. First they eat, and then they say Hallel, for we say Hallel only amidst satiation. This is only if they were answered during their fast.
Why does it say "v'Lo Yevoshu"?
Radak: During the years [of the affliction], they had disgrace of hunger amidst the Goyim.
Malbim: Above (19), it said "you will no longer have Cherpah ba'Goyim." Cherpah is from others; Bushah is what he himself feels. Here it says that they will not be ashamed of their evil deeds, for their sins will be reversed to merits via doing Teshuvah amidst love.
