"Daber Nah B’Aznei HaAm" (Perek Yud Alef Pasuk Bais). Before the beginning of Macas Bechoros (the plague of the first-borns), Hashem tells Moshe that Bnei Yisrael should prepare themselves to leave Egypt. Part of that preparation is going to their Egyptian neighbors and borrowing gold and silver.
Rashi Hakadosh explains that "Nah," meaning please, is an expression of begging. Hashem tells Moshe that Bnei Yisrael should please do this so that Avraham Avinu will not complain that the nation suffered but did not receive their reward. (In the Bris Ben HaBisarim, Hashem told Avraham that Bnei Yisrael would be slaves for 400 years and work hard, but afterward they would leave with great wealth.)
There are two questions that can be asked on this Rashi. The first one is why wouldn’t Bnei Yisrael want to ask for the gold and silver? Why did Hashem have to ask Moshe to seemingly beg them to do it? The second question is why would Avraham come to Hashem and complain? Wouldn’t Avraham just be happy that his children were released from their prison?
The answers are simple. Bnei Yisrael would not want to take the money from the Egyptians because it would assure that they would follow them into the desert. But not taking the money would show that they had a lack of Emunah in Hashem. And that is what Avraham would complain about.
When Hashem told Avraham that Bnei Yisrael would be slaves for 400 years, one of the things Avraham was afraid of was that the nation would lose their Emunah. Hashem asked Moshe to please beg the Am to show Avraham that their Emunah was still strong. And they did. Bnei Yisrael went to the homes of their neighbors and took gold and silver. They did this knowing it would bring the Egyptians after them. After hundreds of years of Galus and great suffering their faith in Hashem was still that strong. It was that trust and Emunah that made them worthy of their Geulah. It will be our faith and Emunah that will make us worthy of ours.