How did Hashem make a remembrance for His wonders?
Rashi: He fixed for Yisrael Shabbosos and Yamim Tovim, about which it says "v'Zacharta Ki Eved Hayisa b'Egypt" (Devarim 16:12).
Radak #1: He did such great wonders in Egypt that they are remembered for all generations.
Radak #2: The wonders that He does in every generation are a remembrance for His first wonders in Egypt.
Malbim: Nifla'os, which are above nature, He does only when there is a need to show His Gevurah to people. This is a remembrance for the generation; they remember that He is the Creator, and He can change the creation.
Why does it say "Chanun v'Rachum Hashem"?
Rashi: He made a remembrance for his wonders because He is gracious and merciful on His children, and wants to vindicate them.
Radak: He was gracious and merciful on [Yisrael].
Malbim: He does these wonders either due to grace, e.g. for the Avos, who found grace in His eyes, or due to mercy, like at the time of Yetzi'as Egypt. He had mercy on their poverty and affliction.
