On March 23, 2014, Pastor Jeff Riddle of Christ Reformed Baptist Church preached a sermon titled 'The Fruit of the Spirit' from Galatians 5:22-26. He makes two observations regarding the singular fruit of the Spirit in verse 22, as opposed to the plural works of the flesh in verse 19.
First, this difference in number indicates that the fruit of the Spirit does not have its source in human deeds or actions in the way that the works of the flesh do. We cannot make ourselves have this fruit; we cannot work up within ourselves a heart of love or of joy or of peace. Just as God gives salvation as an act of His free grace, so He also gives sanctification as an act of His free grace. This is seen by the use of fruit as a metaphor; no one can make fruit appear because it is an inherent part of the plant's nature. Christians produce the fruit of the Spirit because their nature changed when they become a believer. If your nature has changed, then the fruit of the Spirit naturally and organically flows from you; this fruit is consistent with our transformed nature.
Second, if one is a Christian, then he will have all nine of the fruit of the Spirit at the same time because it is a singular, umbrella term. You can't have love without joy, or peace without gentleness. A Christian may not display all aspects of the fruit equally, but if he is saved, he has them growing and developing organically and naturally within him. Therefore, the fruit is different from the gifts of the Spirit, which are different for different Christians. The fruit of the Spirit is something that every Christian has if their nature has been transformed, even though they may not be displaying all aspects of the fruit.
"Ye shall know them by their fruits. Do men gather grapes of thorns, or figs of thistles? Even so every good tree bringeth forth good fruit; but a corrupt tree bringeth forth evil fruit. A good tree cannot bring forth evil fruit, neither can a corrupt tree bring forth good fruit," (Matt. 7:16-18).