James 3:8

But. James draws a sharp contrast between the four classes of wild animals (v. 7) which have been subdued by man, and man’s own tongue, which man himself cannot subdue.

No man. This does not mean that the tongue can never be brought under control, but that sinful human nature lacks the power to subdue it. Man can tame animals, but lacks the power to subdue his own tongue. Divine grace alone can accomplish that. James clearly acknowledges the possibility of taming it (see v. 2), and declares that followers of Christ ought to gain the victory over undisciplined speech (see on v. 10).

Unruly. Textual evidence favors (cf. p. 10) the reading “unsteady,” “restless” (see on James 1:8).

Evil. The tongue is evil only when it is controlled by a mind motivated by the forces of evil. When a man does not let the Holy Spirit control his thoughts, and thus his speech, the tongue functions as an instalment of evil.

Deadly poison. That is, it acts upon the happiness of man and the peace of society, as poison upon the human body. The loss of confidence, peace, and friendship inevitably results from a hasty, ill-advised tongue (cf. Ps. 140:3; Rom. 3:13).