Rashi on Psalms
He made a memorial He set down for Israel Sabbaths and festivals and commandments, of which was stated (Deut. 5:15): “And remember that you were a slave in the land of Egypt,” because He is gracious and merciful to His children, and He wishes to make them righteous.
Metzudat David on Psalms
"He has made a memorial for His wonderful works" - As it is written with regards to the Manna "take a container... and place it...for safe keeping so that it will be a memorial"