Psalm 1 is a wisdom psalm. It sets the tone for the whole book of Psalms. The psalm clearly contrasts the happiness of godly people with the judgment of the wicked. In the end, the way of wisdom will triumph.
The psalm describes an ideal picture of a godly person, similar to Psalm 8. This picture shows what the Lord expects from his people. It also points forward to the coming Messiah, God’s chosen king (Psalm 2).
The people of Israel did not live up to this ideal. The kings from David’s family also failed to meet it. Even the best kings could not bring about the lasting righteousness described in Psalms 1, 2, and 72.
In the New Testament, the apostles use the Psalms to describe the life and work of Jesus the Messiah. Their teaching shows that Jesus alone fulfills the ideal of the godly person described in the Psalms. Only Jesus fully pleased God and secured redemption (rescue from sin), true happiness, and peace.
Psalm 1 also introduces a note of hope that continues through the Psalms. It looks forward to the final hallelujah in Psalm 150). At that time, the Lord will remove all evil from his creation and bring blessing and life to his people.