Matthew 15:16-20
16"Are you still so dull?" Jesus asked them. 17"Don't you see that whatever enters the mouth goes into the stomach and then out of the body? 18But the things that come out of the mouth come from the heart, and these make a man 'unclean.' 19For out of the heart come evil thoughts, murder, adultery, sexual immorality, theft, false testimony, slander. 20These are what make a man 'unclean'; but eating with unwashed hands does not make him 'unclean.' "
Hebrews 3:1
1Therefore, holy brothers, who share in the heavenly calling, fix your thoughts on Jesus, the apostle and high priest whom we confess.
Psalm 139:23,24
23 Search me, O God, and know my heart; test me and know my anxious thoughts. 24 See if there is any offensive way in me, and lead me in the way everlasting.
Philippians 4:8
8Finally, 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.