From Pope St. John Paul II’s encyclical Veritatis Splendor (1993):
E vangelization — and therefore the “new evangelization” — also involves the proclamation and presentation of morality. Jesus himself, even as he preached the Kingdom of God and its saving love, called people to faith and conversion (cf. Mk 1:15). And when Peter, with the other Apostles, proclaimed the Resurrection of Jesus of Nazareth from the dead, he held out a new life to be lived, a “way” to be followed, for those who would be disciples of the Risen One (cf. Acts 2:37-41; 3:17-20).
Just as it does in proclaiming the truths of faith, and even more so in presenting the foundations and content of Christian morality, the new evangelization will show its authenticity and unleash all its missionary force when it is carried out through the gift not only of the word proclaimed but also of the word lived. In particular, the life of holiness which is resplendent in so many members of the People of God, humble and often unseen, constitutes the simplest and most attractive way to perceive at once the beauty of truth, the liberating force of God’s love, and the value of unconditional fidelity to all the demands of the Lord’s law, even in the most difficult situations. For this reason, the Church, as a wise teacher of morality, has always invited believers to seek and to find in the Saints, and above all in the Virgin Mother of God “full of grace” and “all-holy”, the model, the strength and the joy needed to live a life in accordance with God’s commandments and the Beatitudes of the Gospel.
The lives of the saints, as a reflection of the goodness of God — the One who “alone is good” — constitute not only a genuine profession of faith and an incentive for sharing it with others, but also a glorification of God and his infinite holiness. The life of holiness thus brings to full expression and effectiveness the threefold and unitary munus propheticum, sacerdotale et regale which every Christian receives as a gift by being born again “of water and the Spirit” (Jn 3:5) in Baptism. His moral life has the value of a “spiritual worship” (Rom 12:1; cf. Phil 3:3), flowing from and nourished by that inexhaustible source of holiness and glorification of God which is found in the Sacraments, especially in the Eucharist: by sharing in the sacrifice of the Cross, the Christian partakes of Christ’s self-giving love and is equipped and committed to live this same charity in all his thoughts and deeds. In the moral life the Christian’s royal service is also made evident and effective: with the help of grace, the more one obeys the new law of the Holy Spirit, the more one grows in the freedom to which he or she is called by the service of truth, charity and justice.
— Veritatis Splendor 107