From Pope St. John Paul II’s encyclical Veritatis Splendor (1993):
The way and at the same time the content of this perfection consist in the following of Jesus, sequela Christi, once one has given up one’s own wealth and very self. This is precisely the conclusion of Jesus’ conversation with the young man: “Come, follow me” (Mt 19:21). It is an invitation the marvellous grandeur of which will be fully perceived by the disciples after Christ’s Resurrection, when the Holy Spirit leads them to all truth (cf. Jn 16:13).
It is Jesus himself who takes the initiative and calls people to follow him. His call is addressed first to those to whom he entrusts a particular mission, beginning with the Twelve; but it is also clear that every believer is called to be a follower of Christ (cf. Acts 6:1). Following Christ is thus the essential and primordial foundation of Christian morality: just as the people of Israel followed God who led them through the desert towards the Promised Land (cf. Ex 13:21), so every disciple must follow Jesus, towards whom he is drawn by the Father himself (cf. Jn 6:44).
This is not a matter only of disposing oneself to hear a teaching and obediently accepting a commandment. More radically, it involves holding fast to the very person of Jesus, partaking of his life and his destiny, sharing in his free and loving obedience to the will of the Father. By responding in faith and following the one who is Incarnate Wisdom, the disciple of Jesus truly becomes a disciple of God (cf. Jn 6:45). Jesus is indeed the light of the world, the light of life (cf. Jn 8:12). He is the shepherd who leads his sheep and feeds them (cf. Jn 10:11-16); he is the way, and the truth, and the life (cf. Jn 14:6). It is Jesus who leads to the Father, so much so that to see him, the Son, is to see the Father (cf. Jn 14:6-10). And thus to imitate the Son, “the image of the invisible God” (Col 1:15), means to imitate the Father.
— Veritatis Splendor 19