Out of the heart
And indeed, from where should evil thoughts proceed in the servant who is as his Master? Out of the heart of man (if at all) proceed evil thoughts (Mark 7:21). If therefore his heart is no longer evil, then evil thoughts can no longer proceed out of it. If the tree were corrupt, so would be the fruit; but the tree is good (Matthew 12:33). The fruit therefore is good also. Our Lord himself bearing witness: Every good tree brings forth good fruit. A good tree cannot bring forth evil fruit, as a corrupt tree cannot bring forth good fruit (Matthew 7:17-18).
1771 text
22. And indeed, whence should evil thoughts proceed, in the servant who is as his Master? out of the heart of man (if at all) proceed evil thoughts (Mark vii. 21.) If therefore his heart, be no longer evil, then evil thoughts can no longer proceed out of it. If the tree were corrupt, so would be the fruit; but the tree is good. The fruit therefore is good also. (Matth. xii. 33.) Our Lord himself bearing witness, Every good tree bringeth forth good fruit. A good tree cannot bring forth evil fruit, as a corrupt tree cannot bring forth good fruit, Matt. vii. 17, 18.