Tosefta sur Les Psaumes 66:18

A good thought [Hashem] combines to action; a bad thought Hashem does not combine to action, as it is stated, "If I had regarded iniquity in my heart [the Lord would not hear]." How, then, am I to understand "Behold I am bringing evil, fruit of your thoughts?" Rather, a good thought that does good Hashem combines to action, and that which does not do good Hashem does not combine to action.