12. Transition from the mouth to the heart.
      Can the fig tree, &c.--implying that it is an impossibility: as before in Jas 3:10 he had said it "ought not so to be." James does not, as Matthew (Mt 7:16, 17), make the question, "Do men gather figs of thistles?" His argument is, No tree "can" bring forth fruit inconsistent with its nature, as for example, the fig tree, olive berries: so if a man speaks bitterly, and afterwards speaks good words, the latter must be so only seemingly, and in hypocrisy, they cannot be real.
      so can no fountain . . . salt . . . and fresh--The oldest authorities read, "Neither can a salt (water spring) yield fresh." So the mouth that emits cursing, cannot really emit also blessing.

JFB.