The parable of the two trees 6:43-44 (cf. Matt. 7:15-20)

Jesus' point in this parable was that a person of bad character cannot normally produce good conduct (cf. Matt. 12:33-35). Therefore His disciples needed to clean up their lives before they could minister for Him effectively. As a pupil follows the example of his teacher (v. 40), so fruit from a tree follows the nature of its tree. In the Matthew parallel Jesus applied the parable to false teachers, but here it stands by itself and applies in this context to disciples of His. Conduct follows character as surely as fruit follows root, for good and for bad (cf. James 3:12).²¹⁴

"The text indicates that although fruit may not be a certain indicator, it can be a suggestive one."²¹⁵