Romans 2:13-15

13For it is not the hearers of the law who are righteous before God, but it is the doers of the law who will be declared righteous.

14Indeed, when Gentiles, who do not have the law, do by nature what the law requires, they are a law to themselves, even though they do not have the law. 15So they show that the work of the law is written on their hearts, their consciences also bearing witness, and their thoughts either accusing or defending them