19 On the basis of this sharing in Jesus’ way of seeing things, Saint Paul has left us a description of the life of faith. In accepting the gift of faith, believers become a new creation; they receive a new being; as God’s children, they are now "sons in the Son". The phrase "Abba, Father", so characteristic of Jesus’ own experience, now becomes the core of the Christian experience (cf. Rom 8:15). The life of faith, as a filial existence, is the acknowledgment of a primordial and radical gift which upholds our lives. We see this clearly in Saint Paul’s question to the Corinthians: "What have you that you did not receive?" ( 1 Cor 4:7). This was at the very heart of Paul’s debate with the Pharisees: the issue of whether salvation is attained by faith or by the works of the law. Paul rejects the attitude of those who would consider themselves justified before God on the basis of their own works. Such people, even when they obey the commandments and do good works, are centred on themselves; they fail to realize that goodness comes from God. Those who live this way, who want to be the source of their own righteousness, find that the latter is soon depleted and that they are unable even to keep the law. They become closed in on themselves and isolated from the Lord and from others; their lives become futile and their works barren, like a tree far from water. Saint Augustine tells us in his usual concise and striking way: " Ab eo qui fecit te, noli deficere nec ad te ", "Do not turn away from the one who made you, even to turn towards yourself". Once I think that by turning away from God I will find myself, my life begins to fall apart (cf. Lk 15:11-24). The beginning of salvation is openness to something prior to ourselves, to a primordial gift that affirms life and sustains it in being. Only by being open to and acknowledging this gift can we be transformed, experience salvation and bear good fruit. Salvation by faith means recognizing the primacy of God’s gift. As Saint Paul puts it: "By grace you have been saved through faith, and this is not your own doing; it is the gift of God" ( Eph 2:8).
Source: Lumen Fidei (Vatican.va)