Can a fig tree, my brothers, bear olives, or a grapevine produce figs? Neither can a salt pond yield fresh water.
The foregoing chapter shows how unprofitable and dead faith is without works. It is plainly intimated by what this chapter first goes upon that such a faith is, however, apt to make men conceited and magisterial in their tempers and their talk. Those who set up faith in the manner the former chapter condemns are most apt to run into those sins of the tongue which this chapter condemns.
Commenting on James 3:1-12
Can the fig tree, my brethren, bear olive berries?.... Every tree bears fruit, according to its kind; a fig tree produces figs, and an olive tree olive berries; a fig tree does not produce olive berries, or an olive tree figs; and neither of them both: either a vine, figs?
Verse 12. Can the fig-tree, my brethren, bear olive berries? Such a thing is impossible in nature, and equally absurd in morals. A fig-tree bears only figs; and so the tongue ought to give utterance only to one class of sentiments and emotions. These illustrations are very striking, and show the absurdity of that which the apostle reproves.