From the pastoral constitution on the Church in the modern world of the Second Vatican Council
I am Alpha and Omega, the first and the last
The way in which the earthly and the heavenly city interpenetrate each other can be recognized only by faith; indeed, it remains a mystery of human history, that is, of a history always troubled by sin until the glory of the sons of God is fully revealed.
As she pursues her appointed goal of bringing salvation to men, the Church not only communicates the divine life to mankind but also in some measure reflects the light of that life over the whole world. She does this especially through her work of restoring and enhancing the dignity of the human person, of strengthening the fabric of human society, and of enriching the daily activity of men with a deeper meaning and importance. The Church believes that in this way she can make a great contribution, through individual members and the community as a whole, toward bringing a greater humanity to the family of man and to its history.
While the Church helps the world and herself receives much from the world, she has one object in view: the coming of God's kingdom and the salvation of the whole human race. Every good that the people of God in the course of its earthly pilgrimage can confer on the family of men derives from the fact that the Church is the universal sacrament of salvation, revealing, and at the same time bringing into operation, the mystery of God's love for man.
The Word of God, through whom all things were made, was himself made flesh so that as perfect man he might save all men and bring all things into unity. The Lord is the final end of human history, the point toward which the aspirations of history and civilization are moving, the focus of the human race, the joy of all hearts and the fulfillment of their desires. He it is whom the Father raised from the dead, lifted up on high and set at his right hand, appointing him judge of the living and the dead. In his Spirit we have been brought to life and gathered into unity, and so make our pilgrim way toward the goal of human history, a goal in complete harmony with the loving plan of God to make all things one in Christ, the things in heaven and the things on earth.
The Lord himself says: See, I am coming soon; I bring my recompense with me, to give to everyone what his deeds deserve. I am Alpha and Omega, the first and the last, the beginning and the end.