First, since all true believers, those who abide in Christ and He in them, will bear spiritual fruit, there is no such thing as a fruitless Christian. John the Baptist challenged his hearers to “bear fruit in keeping with repentance” (Matt. 3:8), and warned that “every tree that does not bear good fruit is cut down and thrown into the fire” (v. 10). Contrasting true and false teachers, Jesus said, “Every good tree bears good fruit, but the bad tree bears bad fruit. A good tree cannot produce bad fruit, nor can a bad tree produce good fruit. Every tree that does not bear good fruit is cut down and thrown into the fire. So then, you will know them by their fruits” (Matt. 7:17–20). In Luke 6:43 He added, “There is no good tree which produces bad fruit, nor, on the other hand, a bad tree which produces good fruit.”
MacArthur New Testament Commentary
4 The central focus of Jesus’ teaching in this opening paragraph is found here: “Remain in me, and I will remain in you.” Since a verb must be supplied in the Greek text for the second clause, the NIV adds, “will remain.” Moffatt has, “as I remain in you.” Morris, 670, favors taking the second clause as a continuation of the command in the first clause and translates, “and see that I abide in you.” A more satisfactory approach is to allow the ambiguous relationship between the clauses to remain and to see in the sentence as a whole the dual condition that we as believers are to bring into being. Jesus is setting before us the prospect of the mutual indwelling of Jesus and those who will abide in him. So central is this mutual indwelling to what it means to be a Christian that Temple, 2:258, can say, “Whatever leads to this is good; whatever hinders this is bad; whatever does not bear on this is futile.”
The verb “remain” occurs ten times in the first eleven verses of ch. 15. For a branch to bear fruit it must share the life of the vine. Likewise, for believers to bear fruit they must remain in Christ. All spiritual power for living out the Christian life comes from God. There is only one way for a believer to receive this power, namely, to remain in unbroken fellowship with the source of power. Paul pictures the relationship in terms of a spiritual death and resurrection: “I have been crucified with Christ and I no longer live, but Christ lives in me” (Gal 2:20).
Expositor’s Bible Commentary