O Rex Gentium: “O King of all the nations, the only joy of every human heart; O Keystone of the mighty arch of man, come and save the creature you fashioned from the dust.” Isaiah had prophesied, “For a child is born to us, a son is given us; upon his shoulder dominion rests. They name him Wonder-Counselor, God-Hero, Father-Forever, Prince of Peace.” (9:5), and “He shall judge between the nations, and impose terms on many peoples. They shall beat their swords into plowshares and their spears into pruning hooks; one nation shall not raise the sword against another, nor shall they train for war again.” (2:4) .

~ Fr. William Sanders

Christ’s birth made the corner-stone of two walls in a building: here representing Jews and Gentiles, and thus ushered in salvation for all people. Remember those Greeks who came to Jerusalem seeking Jesus in the Johannine Gospel. Christ is not only the corner stone binding all creatures but He is also king of the nations. This antiphon should also be a reminder of our humble beginning brought into existence by the breath of God. Today we pray that the news of a saviour and ruler will be heard by all, wherever they live and however they live.
O Rex Gentium, although you took our human flesh to make us all brothers and sisters in you, you are also our Ruler; Come O Holy Spirit, help us to acknowledge Christ as our Sovereign,  and lead all footsteps to the Christ this Christmas. Amen.
                                                                                                                                                         ~ http://mariannedorman.homestead.com