http://revach.net/article.php?id=2139

Section: Moadim   Category: Hagadah Shel Pesach
The Great Promise To Avrohom, Rechush Gadol!
The Bnei Yisroel “borrowed” from their Mitzri neighbors all their valuables so that Avrohom will not complain to Hashem that Hashem enslaved them in a foreign land in accordance with His promise made at the Bris Bein HaBesarim but not the promise of leaving with great wealth.  This begs two questions.  First why did Avrohom care about the money?  Second why did Hashem keep His promise so that Avrohom shouldn’t complain?  Shouldn’t Hashem keep His promise whether Avrohom complains or not?

The Alshich HaKadosh says that in fact the “Rechush Gadol” that Hashem promised was the spiritual level that enslavement in Mitzrayim would help them reach and not material wealth.  He proves this by the fact that the torah uses the words Rechush “Gadol” meaning big and great.  Had it referred to material wealth it should have said Rechush “Rav” abundant wealth. 

Therefore explains the Chidushei HaRim, as far as Hashem was concerned His promised was kept to Avrohom by giving Bnei Yisroel the torah and not by giving them the wealth of Mitzrayim.  However Hashem was concerned that Avrohom would complain that just like when Hashem promised enslavement it turned out to be both physical and spiritual, so too should the riches that they receive at the redemption be both physical and spiritual. (Hagadah Otzar HaMedrashim)