(Recycled from 2012)
O King of the nations, only joy of every human heart; O Keystone of the mighty arch of man, come save the creature you fashioned from the dust.
In stonemasonry, the block at the apex of an arch is called the keystone. An arch cannot support itself without the keystone; the pressure the keystone exerts holds the arch in place and allows it to bear weight. Truly, Christ is our keystone: He is the head, the Church His mystical body. He gives us life, holding us in existence. With God, we are strong ("I can do all things through Christ who strengthens me." Phil 4:13); without Him, we crumble back to the dust from whence we came.
Only in Christ, the king of all nations, can all nations of the world be brought together in peace; the "arch of man," the coming together of all humanity, cannot hold together or bear weight without Him.
O come, desire of nations, bind
In one the hearts of all mankind.
Bid Thou our sad divisions cease
And fill the world with heaven's peace.
Rejoice, rejoice; Emmanuel shall come to thee, O Israel.