Think before you speak and reveal your ignorance. It's in the Bible, Proverbs 15:28, TLB. "A good man thinks before he speaks; the evil man pours out his evil words without a thought."
We should discipline our thoughts to be pure—because actions begin in the heart. It's in the Bible, Mark 7:21-22, TLB. "For from within, out of men's hearts, come evil thoughts of lust, theft, murder, adultery, wanting what belongs to others, wickedness, deceit, lewdness, envy, slander, pride, and all other folly." Proverbs 23:7, NKJV says, "For as he thinks in his heart, so is he "
After conversion, we must allow the Holy Spirit to change our thought patterns. It's in the Bible, Romans 12:2, TLB. "Don't copy the behavior and customs of this world, but be a new and different person with a fresh newness in all you do and think. Then you will learn from your own experience how His ways will really satisfy you."
We should think about good things so our words and actions will be positive and wise. It's in the Bible, Philippians 4:8, NIV. "Finally, brothers, whatever is true, whatever is noble, whatever is right, whatever is pure, whatever is lovely, whatever is admirable—if anything is excellent or praiseworthy—think about such things."
We should let Christ mind be in us. It's in the Bible, Philippians 2:5, NRSV. "Let the same mind be in you that was in Christ Jesus."