The thoughts of the wicked are an abomination to YHVH, but gracious words are pure.
Proverbs 15:26

Thoughts eventually come out in words and then in deeds. They are the first seeds of an unclean heart. See the Sermon on the Mount and Yeshua's statements about hatred and lust being tantamount to murder and adultery in the eyes of God, and also that "blessed are the peacemakers".