What does the Bible say about guarding my tongue?

In Psalm 141:3, David prays for God to set a watch over his mouth, recognizing the potential damage that uncontrolled speech can cause. James 3:6-8 elaborates on this by describing the tongue as a restless evil, full of deadly poison, which no one can tame. The necessity of asking God for restraint is echoic of the understanding that our tongues can not only bring pain but also discord amongst believers. Thus, believers are encouraged to speak words that are uplifting and representative of God's grace, reflecting Christ's example in their speech.