Commentaries:
The construction here reinforces the meaning. It is not just "forever" but "forever and ever" that His commandments stand fast. Does that sound like God would to do away with His law? If they stand fast, nothing can move them, regardless of how many people say, "The law is done away."
John W. Ritenbaugh
The Covenants, Grace, and Law (Part Ten)
It is important to understand when researchers feel this psalm was written: sometime after the Jews returned from their exile in Babylon. In other words, during the time of Nehemiah and Ezra or perhaps shortly thereafter. We should imagine a scribe (someone like Ezra) writing this psalm, extolling how God once again redeemed His people from slavery, brought them back to their land, and supplied their every need.
John W. Ritenbaugh
The Covenants, Grace, and Law (Part Ten)