By contrast the beautiful list that follows contains characteristics which belong only to the child of God. They are called the fruit of the Spirit because they are the product of the Spirit’s work in the believer’s heart, and come from that new nature which is the opposite of the flesh described in the previous three verses.
Why it is that the fruit of the Spirit are found only in converted men and women? Cannot unbelievers also produce these same fruit in their lives? No, they can produce only something that has the outward form but not a single true work acceptable to God. The new nature has what is not present in the unbeliever: a genuine desire to please God out of love for him and gratitude for salvation already received.
At times Scripture speaks about the believer’s new nature, but in this passage Paul refers to the source of this fruit as the Spirit. This is not because the Spirit so takes over the fight for us that we are unaware of it, or not involved. No, it is our resisting of temptation and our striving for good that he is talking about, since it is clear that he is describing a contest within our own hearts. The lusting of the Spirit is just as much our own as the lusting of the flesh, and we feel the battle. But he calls the new nature by the name of the Spirit because without the constant activity of the Spirit, this nature could not operate.