Sometimes daring to believe in opposition to the values around us means believing the gospel even in contrast to the practice of Christianity we see around us! These people dare to make a difference in the world for the name of their Lord Jesus. Jesus already understood what many of us who work for him have yet to learn: in the long run, drawing crowds is less significant for the kingdom than training those who will multiply the work by training others in turn. Perhaps many of us prefer numbers in the short term over spiritual depth because we lack the faith to believe that such depth is essential (compare v. 12); but fifty disciples with spiritual depth will produce greater numbers in the end than a million raised hands without commitment ever could.
We should take careful note, however, of Matthew’s description of the fruitful person: the fruitful person is the one who understands the message (v. 23). Only those who press close to Jesus, persevering until they understand the real point of his teaching, will prove to be long-term disciples (vv. 10-17; compare Jn 8:31-32; Marshall 1974:62-63).
–from his Matthew IVP New Testament Commentary