“And he arose, and came to his father. But when he was a great way off, his father saw him, and had compassion for him, and ran, and fell on his neck, and kissed him.” Luke 15:20
You probably know the setup in the preceding verses of Luke 15. The younger son has come to his senses and decided to return to his father, rehearsing along the way a speech where he says that due to his sin, he is no longer worthy to be a son, but is offering himself as a “hired servant” that he might not starve to death. You can almost hear him as he practices the speech on the way home: “I am no more worthy to be called thy son: make me as one of thy hired servants.” Luke 15:19 But it is a speech the younger son never gets to deliver because, as noted in the opening passage, the father has a different plan. On the younger son’s return, before he can utter a word, the father runs out to meet the errant son, welcomes him back, and orders the servants (which the younger son was prepared to become) to bring the younger son a robe, shoes, and a ring.
All that to say that the son is not made perfect through anything he has done. The son is (can only be) made perfect through the father. So he/it is. Truth be told, human imperfection is a given, and perfection (grace) only comes through the father.