We can read this psalm in its historical context. A few kings had praise-worthy reigns. Most did not. Psalm 72 is a prayer that the new king will be one of those who carries out the role the way the Lord would have intended for a king to do.
And we can read this psalm in our own time and place. I am a citizen of a country that eschewed the monarchy over two centuries ago. But, the qualities of a king in this psalm are certainly the qualities we would pray for in our elected leaders.
I have done so myself. Several years ago, a member of the local church I was serving asked me to attend and say grace for a breakfast and for a mayoral candidate. Even though as a minister, I was not willing to make an endorsement in an election, I was and am willing to pray for leaders and prospective leaders. I read portions of this psalm before giving the blessing to the meal, including verses 1 through 4.
In Advent this week, we are reading this psalm in response to the description in Isaiah of the leader who is promised--and a description of what this leader's kingdom (I really ought to learn how to substitute "reign") will be like. The vision is one of peace, peace among natural enemies.
Psalm 72 asks that God give the king justice and righteousness. Note what righteousness means--defending the cause of the poor, giving deliverance to the needy, and crushing the oppressor.
In Advent, as we look forward to the coming of Christ, let us hope for, let us pray for a world in which the poor and needy are cared for and oppression is crushed.
And, while we are waiting, we need to assume some of these kingly responsibilities ourselves. The poor and needy don't need to be kept waiting. Neither does oppression.