39 We do not know the time for the consummation of the earth and of humanity, nor do we know how all things will be transformed. As deformed by sin, the shape of this world will pass away; but we are taught that God is preparing a new dwelling place and a new earth where justice will abide, and whose blessedness will answer and surpass all the longings for peace which spring up in the human heart. Then, with death overcome, the sons of God will be raised up in Christ, and what was sown in weakness and corruption will be invested with incorruptibility. Enduring with charity and its fruits, all that creation which God made on man's account will be unchained from the bondage of vanity. Therefore, while we are warned that it profits a man nothing if he gain the whole world and lose himself, the expectation of a new earth must not weaken but rather stimulate our concern for cultivating this one. For here grows the body of a new human family, a body which even now is able to give some kind of foreshadowing of the new age. Hence, while earthly progress must be carefully distinguished from the growth of Christ's kingdom, to the extent that the former can contribute to the better ordering of human society, it is of vital concern to the Kingdom of God. For after we have obeyed the Lord, and in His Spirit nurtured on earth the values of human dignity, brotherhood and freedom, and indeed all the good fruits of our nature and enterprise, we will find them again, but freed of stain, burnished and transfigured, when Christ hands over to the Father: "a kingdom eternal and universal, a kingdom of truth and life, of holiness and grace, of justice, love and peace." On this earth that Kingdom is already present in mystery. When the Lord returns it will be brought into full flower.
Source: Gaudium et Spes (Vatican.va)