The parable of the two sons in Matthew 21 deals with "true faith" that requires "action" or "practice." The father has a vineyard that needs workers. The first son says first, no, but later he changed his mind and went to work. He is not perfect but did the will of the father. The second son: first, yes, but he never went to work. He did not obey his father. Word only does not help. The perfect son will be the one who says “yes” and goes to work immediately. Jesus points out the problem of hypocrites, who don’t do what they know or teach (Matt 23:3).