18 Those who live "by the flesh" experience God's law as a burden, and indeed as a denial or at least a restriction of their own freedom. On the other hand, those who are impelled by love and "walk by the Spirit" ( Gal 5:16), and who desire to serve others, find in God's Law the fundamental and necessary way in which to practise love as something freely chosen and freely lived out. Indeed, they feel an interior urge — a genuine "necessity" and no longer a form of coercion — not to stop at the minimum demands of the Law, but to live them in their "fullness". This is a still uncertain and fragile journey as long as we are on earth, but it is one made possible by grace, which enables us to possess the full freedom of the children of God (cf. Rom 8:21) and thus to live our moral life in a way worthy of our sublime vocation as "sons in the Son". This vocation to perfect love is not restricted to a small group of individuals. The invitation, "go, sell your possessions and give the money to the poor", and the promise "you will have treasure in heaven", are meant for everyone, because they bring out the full meaning of the commandment of love for neighbour, just as the invitation which follows, "Come, follow me", is the new, specific form of the commandment of love of God. Both the commandments and Jesus' invitation to the rich young man stand at the service of a single and indivisible charity, which spontaneously tends towards that perfection whose measure is God alone: "You, therefore, must be perfect, as your heavenly Father is perfect" ( Mt 5:48). In the Gospel of Luke, Jesus makes even clearer the meaning of this perfection: "Be merciful, even as your Father is merciful" ( Lk 6:36).
Source: Veritatis Splendor (Vatican.va)