Joyful arrival and prayer for Jerusalem's peace

Gladness is the sound of being asked to go up together

I was glad when they said unto me, Let us go into the house of the LORD. Our feet shall stand within thy gates, O Jerusalem. Jerusalem is builded as a city that is compact together: whither the tribes go up, the tribes of the LORD, unto the testimony of Israel, to give thanks unto the name of the LORD.

The pilgrim is glad at a communal invitation, not at a private vision. Feet standing in the gates is arrival. Compact together pictures a tightly joined city, tribes going up to the testimony—the appointed worship—to give thanks. Thrones of judgment, the thrones of the house of David, sit in that city: worship and just decision are supposed to share a place.

Peace for Jerusalem is asked for brothers' sake, not as a slogan

Pray for the peace of Jerusalem: they shall prosper that love thee. Peace be within thy walls, and prosperity within thy palaces. For my brethren and companions' sakes, I will now say, Peace be within thee. Because of the house of the LORD our God I will seek thy good.

Shalom and prosperity are wished inside walls and palaces. The motives named are brethren, companions, and the house of the LORD. The psalm is a pilgrim's love of the city as the place of gathering and judgment. It is not a modern foreign-policy plank, not a blank check for any later skyline called Jerusalem, and not a permission to ignore people who live there now as if they were scenery.