161. It would not be right to see this call to growth exclusively or primarily in terms of doctrinal formation. It has to do with “observing” all that the Lord has shown us as the way of responding to his love. Along with the virtues, this means above all the new commandment, the first and the greatest of the commandments, and the one that best identifies us as Christ’s disciples: “This is my commandment, that you love one another as I have loved you” (Jn 15:12). Clearly, whenever the New Testament authors want to present the heart of the Christian moral message, they present the essential requirement of love for one’s neighbor: “The one who loves his neighbor has fulfilled the whole law… therefore love of neighbor is the fulfilling of the law” (Rom 13:8, 10). These are the words of Saint Paul, for whom the commandment of love not only sums up the law but constitutes its very heart and purpose: “For the whole law is fulfilled in one word, ‘you shall love your neighbor as yourself’” (Gal 5:14). To his communities Paul presents the Christian life as a journey of growth in love: “May the Lord make you increase and abound in love for one another and for all” (1 Th 3:12). Saint James likewise exhorts Christians to fulfill “the royal law according to the Scripture: You shall love your neighbor as yourself” (2:8), in order not to fall short of any commandment.
162. On the other hand this process of response and growth is always preceded by God’s gift, since the Lord first says: “Baptize them in the name…” (Mt 28:19). The Father’s free gift which makes us his sons and daughters, and the priority of the gift of his grace (cf. Eph 2:8-9; 1 Cor 4:7), enable that constant sanctification which pleases God and gives him glory. In this way, we allow ourselves to be transformed in Christ through a life lived “according to the Spirit” (Rom 8:5).
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