17:5 Luke referred to the Twelve as apostles here probably to highlight the importance of this teaching for disciple leaders. Evidently the apostles concluded that such a magnanimous approach to forgiving would require more faith in God than they possessed. They would have to believe that God could change a person's heart who gave no evidence of genuine contrition by repeatedly sinning and then repeatedly professing repentance.
17:6 Jesus encouraged the disciples by reminding them that only a little trust in God's ability can result in unbelievable change (cf. Matt. 17:20; 21:21; Mark 11:23). A mustard seed was proverbially small (cf. 7:13). Mulberry trees grew to be as tall as 35 feet and were difficult to uproot.386This response by Jesus amounted to telling the disciples that they did not need more faith. They just needed to use the faith they had.
"This word of Jesus does not invite Christians to become conjurers and magicians, but heroes like those whose exploits are celebrated in the eleventh chapter of Hebrews."387
