60 Everyone realizes, of course, that God our Redeemer founded this society which was to endure to the end of time, for as Christ said, "Behold, I am with you all days, even unto the consummation of the world."(18) For this intention He addressed ardent prayers to His Father: "That all may be one, even as thou, Father, in me and I in thee; that they also may be one in Us."(19) Surely this prayer was heard and granted because of His reverent submission.(20) This is a comforting hope; it assures us that someday all the sheep who are not of this fold will want to return to it. Then, in the words of God our Savior, "there shall be one fold and one shepherd."(21)
Source: Ad Petri Cathedram (Vatican.va)