The KJV rendering of Psalm 5:3 can give one the impression that this is a prayer of general devotion to be recited in the morning. However, a careful reading of the psalm shows that quite a bit more is going on here.
Psalm 2 is a celebration of the unquestionable supremacy of God and his Messiah over all the rebellious forces of humanity. Not only is this the message of the Psalm’s content, it is even embedded in the Psalm’s concentric structure.
Commentaries are helpful, but the proper posture towards them, regardless of your knowledge of scholarship in the field, is one of resistance. By asking “How do we know that?”, you are positioning yourself to get the most out of your conversation with the Bible and out of the commentary.