From Pope St. John Paul II’s encyclical Veritatis Splendor (1993):
There is no doubt that Christian moral teaching, even in its Biblical roots, acknowledges the specific importance of a fundamental choice which qualifies the moral life and engages freedom on a radical level before God. It is a question of the decision of faith, of the obedience of faith (cf. Rom 16:26) “by which man makes a total and free self-commitment to God, offering ‘the full submission of intellect and will to God as he reveals'”.112 This faith, which works through love (cf. Gal 5:6), comes from the core of man, from his “heart” (cf. Rom 10:10), whence it is called to bear fruit in works (cf. Mt 12:33-35; Lk 6:43-45; Rom 8:5-10; Gal 5:22). In the Decalogue one finds, as an introduction to the various commandments, the basic clause: “I am the Lord your God . . .” (Ex 20:2), which, by impressing upon the numerous and varied particular prescriptions their primordial meaning, gives the morality of the Covenant its aspect of completeness, unity and profundity. Israel’s fundamental decision, then, is about the fundamental commandment (cf. Jos 24:14-25; Ex 19:3-8; Mic 6:8). The morality of the New Covenant is similarly dominated by the fundamental call of Jesus to follow him — thus he also says to the young man: “If you wish to be perfect . . . then come, follow me” (Mt 19:21); to this call the disciple must respond with a radical decision and choice. The Gospel parables of the treasure and the pearl of great price, for which one sells all one’s possessions, are eloquent and effective images of the radical and unconditional nature of the decision demanded by the Kingdom of God. The radical nature of the decision to follow Jesus is admirably expressed in his own words: “Whoever would save his life will lose it; and whoever loses his life for my sake and the Gospel’s will save it” (Mk 8:35).
Jesus’ call to “come, follow me” marks the greatest possible exaltation of human freedom, yet at the same time it witnesses to the truth and to the obligation of acts of faith and of decisions which can be described as involving a fundamental option. We find a similar exaltation of human freedom in the words of Saint Paul: “You were called to freedom, brethren” (Gal 5:13). But the Apostle immediately adds a grave warning: “Only do not use your freedom as an opportunity for the flesh”. This warning echoes his earlier words: “For freedom Christ has set us free; stand fast therefore, and do not submit again to a yoke of slavery” (Gal 5:1). Paul encourages us to be watchful, because freedom is always threatened by slavery. And this is precisely the case when an act of faith — in the sense of a fundamental option — becomes separated from the choice of particular acts, as in the tendencies mentioned above.
112 Second Vatican Ecumenical Council, Dogmatic Constitution on Divine Revelation, Dei Verbum, 5; cf. First Vatican Ecumenical Council, Dogmatic Constitution on the Catholic Faith Dei Filius, Chap. 3: H. Denzinger-A. Schönmetzer, Enchiridion Symbolorum Definitionum et Declarationum de Rebus Fidei et Morum, 3008.
— Veritatis Splendor 66