In the Lukan parable of the Prodigal Son (Lk. 15:11–32), the father might very well have adopted other means for the rehabilitation of his younger son than those described (with approval) by Jesus. When the black sheep of the family came home in disgrace, the father, having a father’s heart, might well have consented to give him a second chance. Listening to his carefully rehearsed speech, he might have said, ‘That’s all very well, young man, we have heard fine phrases before. If you really mean what you say, you can buckle to and work as you have never worked before, and if you do so, we may let you work your passage. But first you must prove yourself; we can’t let by-gones be by-gones as though nothing had happened.’ Even that would have been generous; it might have done the young man a world of good, and even the elder brother might have been content to let him be put on probation. But for Jesus, and for Paul, divine grace does not operate like that. God does not put repentant sinners on probation to see how they will turn out; he gives then an unrestrained welcome and invests them as his true-born sons. For Jesus, and for Paul, the initiative always rests with the grace of God. He bestows the reconciliation or redemption; men receive it. ‘Treat me as one of your hired servants’, says the prodigal to his father; but the father speaks of him as ‘this my son’. So, says Paul, ‘through God you are no longer a slave but a son, and if a son then an heir’ (Gal. 4:7).
F. F. Bruce, The Epistle to the Galatians: A Commentary on the Greek Text, New International Greek Testament Commentary (Grand Rapids, MI: W.B. Eerdmans Pub. Co., 1982), 38–39.