"What has revealed the love of God among us is that the Father has sent into the world His only-begotten Son, so that, being made man, He might by His redemption give new life to the entire human race and unify it. Before offering Himself up as a spotless victim upon the altar, Christ prayed to His Father for all who believe in Him: "that they all may be one; even as thou, Father, art in me, and I in thee, that they also may be one in us, so that the world may believe that thou has sent me". In His Church He instituted the wonderful sacrament of the Eucharist by which the unity of His Church is both signified and made a reality. He gave His followers a new commandment to love one another, and promised the Spirit, their Advocate, who, as Lord and life-giver, should remain with them forever" [UNITATIS REDINTEGRATIO, 2].
“I pray not only for them, but also for those who will believe in me through their word, so that they may all be one, as you, Father, are in me and I in you, that they also may be in us, that the world may believe that you sent me. And I have given them the glory you gave me, so that they may be one, as we are one, I in them and you in me, that they may be brought to perfection as one, that the world may know that you sent me, and that you loved them even as you loved me" [John 17:21-24].
"The Church . . . is held, as a matter of faith, to be unfailingly holy. This is because Christ, the Son of God, who with the Father and the Spirit is hailed as 'alone holy,' loved the Church as his Bride, giving himself up for her so as to sanctify her; he joined her to himself as his body and endowed her with the gift of the Holy Spirit for the glory of God." The Church, then, is "the holy People of God," and her members are called "saints."
United with Christ, the Church is sanctified by him; through him and with him she becomes sanctifying. "All the activities of the Church are directed, as toward their end, to the sanctification of men in Christ and the glorification of God." It is in the Church that "the fullness of the means of salvation" has been deposited. It is in her that "by the grace of God we acquire holiness."294
"The Church on earth is endowed already with a sanctity that is real though imperfect." In her members perfect holiness is something yet to be acquired: "Strengthened by so many and such great means of salvation, all the faithful, whatever their condition or state - though each in his own way - are called by the Lord to that perfection of sanctity by which the Father himself is perfect."
Charity is the soul of the holiness to which all are called: it "governs, shapes, and perfects all the means of sanctification [CATECHISM OF THE CATHOLIC CHURCH, 823-826].
All men are called to belong to the new people of God. Wherefore this people, while remaining one and only one, is to be spread throughout the whole world and must exist in all ages, so that the decree of God's will may be fulfilled. In the beginning God made human nature one and decreed that all His children, scattered as they were, would finally be gathered together as one. It was for this purpose that God sent His Son, whom He appointed heir of all things,(118) that be might be teacher, king and priest of all, the head of the new and universal people of the sons of God. For this too God sent the Spirit of His Son as Lord and Life-giver. He it is who brings together the whole Church and each and every one of those who believe, and who is the well-spring of their unity in the teaching of the apostles and in fellowship, in the breaking of bread and in prayers [LUMEN GENTIUM, 13].
Father, all-powerful and ever-living God, we do well always and everywhere to give You thanks.
You are the eternal shepherd Who never leaves His flock untended. Through the apostles you watch over us and protect us always. You made them shepherds of the flock to share in the work of Your Son, and from their place in heaven they guide us still.
And so with all the choirs of angels in heaven we proclaim your glory and join in their unending hymn of praise:
Holy, holy, holy Lord, God of power and might, heaven and earth are full of your glory. Hosanna in the highest. Blessed is he who comes in the name of the Lord. Hosanna in the highest.