Commentaries:
"The assembly of the upright" and "the congregation" are not necessarily different. It is a parallelism in which the one reinforces the other. It is very clear before whom God is going to be praised.
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)