9 With it we bless our God and Father, and with it we curse men, who have been made in the similitude of God. 10 Out of the same mouth proceed blessing and cursing. My brethren, these things ought not to be so. 11 Does a spring send forth fresh water and bitter from the same opening? 12 Can a fig tree, my brethren, bear olives, or a grapevine bear figs? Thus no spring yields both salt water and fresh.” (James 3:9–12, NKJV)
A double-tongue (we are not talking about how to blow a trumpet) is morally repugnant (“these things ought not to be so”) to God. It ought to be so to us. With it, a person praises God while also speaking harmful criticisms against people. Since our words proceed from our hearts, this is ultimately a condemnation of the duplicitous heart. The self-righteous person is found to be such (see Lk. 18:9-12). Yet, “out of the abundance of the heart the mouth speaks” (Matt. 12:34). The consistency of nature (water, trees and vines) reflects the relationship between the heart and the tongue. Just as James warned of the spiritual instability of the “double-minded man” in James 1:7-8, and exhorted the doubled-minded to purify their hearts in James 4:8, he now warns us of being deceived by our very words. Keep your tongue under the control of truth by keeping your heart under the control of truth.