Here is the second-last of the Church’s great O Antiphons:
O Rex Gentium,
et desideratus earum,
lapisque angularis, qui facis utraque unum:
veni et salva hominem,
quem de limo formasti.
And my English translation:
O King of the nations,
and their [unique] Desire,
Cornerstone, who makes the two of them one,
come and save man,
whom you have formed out of clay.
Today’s O Antiphon at Vespers is the second one to begin with an “R”. O Rex Gentium! Christ is the King of all nations and all peoples. The antiphon says that Christ has made the two into one. What does this mean? “The two” are the Jewish and the Gentile peoples. They were previously separated under the Old Covenant Law (the Old Testament). Christ, who is Himself the New Covenant (“This is the Chalice of My Blood, the Blood of the New and Eternal Covenant”) has henceforth made them into a single, united people: the People of God.
May Christ come and save mankind, for He formed us out of clay (or dust). We are thus nothing, but for the grace of God. We have need of His salvation.
You can listen to this antiphon chanted here (not my video or singing):