“From the same mouth come blessing and cursing. My brothers, these things ought not to be so. Does a spring pour forth from the same opening both fresh and salt water? Can a fig tree, my brothers, bear olives, or a grapevine produce figs? Neither can a salt pond yield fresh water.” (James 3:10-12)
For God to win over our speech, he needs to win over our hearts. Ultimately, we need him to change the salt pond into fresh water. This is what James talks about in chapter 1—the new birth (1:18). This can only happen through the Gospel.
We can be faithful in our speech, because Jesus was silent before his oppressors. They hurled accusations at him. And we were there, at the foot of the cross, using our tongues to curse the Lord of Glory and spit in his face. He opened not his mouth. He was silent, except for the moments he spoke words of grace and forgiveness and committed himself to his Father.
And as he hung, pinned to Calvary’s tree, he was rescuing us from the penalty and the destruction of our sin—including the sinful words we’ve spoken.