Matthew 15:19
For evil thoughts, murder, extramarital affairs, sexual immorality, stealing, perjury, slander --- [all these] come from a person's heart,
Acts 8:22
So, repent [i.e., change your heart and life] of such a terrible thing and pray for the Lord to forgive you for even thinking of such a thing. Perhaps He will [if you are really sincere].
Matthew 5:28
But I say to you, everyone who looks at a woman with an improper sexual desire for her [body], has already been sexually unfaithful to his mate in his heart.
Matthew 9:4
Knowing what they were thinking, Jesus said, "Why are you having such evil thoughts in your minds?
2 Corinthians 10:5
We overthrow [vain] reasonings and every lofty idea raised against the knowledge of God [i.e., as revealed through the Gospel], and take captive [our] every thought to [make it] obey Christ.