Psalms - Chapter 2
Psalm 1 (continued)
The Talmud (Brachos 10b) says that Psalm 2 is a continuation of Psalm 1. David asks why people gather to plot pointlessly. They conspire against G-d and His anointed one (David himself). G-d will laugh at their efforts and when He responds to their attempts in anger, they will be terrified.
G-d says that He has appointed David as His king over Israel, so the nations have no right to interfere. David acknowledges that G-d has treated him as a son. If David just asked, G-d would give him dominion over the other nations.
Because of this, the kings of other nations are advised to play it smart. They should humbly serve G-d, even while trembling before Him. They should strive to be pure in order not to incur G-d's wrath; fortunate are those who trust in Him.