James 3:7-12 (ESV)
For every kind of beast and bird, of reptile and sea creature, can be tamed and has been tamed by mankind,  but no human being can tame the tongue. It is a restless evil, full of deadly poison.  With it we bless our Lord and Father, and with it we curse people who are made in the likeness of God.  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.
Perhaps these things ought not be so, but they are. As James himself says, no human being can tame the tongue. Our tongues are dangerous. And the fact that we use the same one to curse our neighbor as we do to bless our Lord, well now we understand why nothing we do is good outside of Christ, its all tainted with sin, because we are sinners, and grapevines don’t produce figs.