Romans 2:12-16

12 All who have sinned apart from the law will also perish apart from the law, and all who have sinned under the law will be judged by the law.
13 For it is not the hearers of the law who are righteous in God's sight, but the doers of the law who will be justified.
14 When Gentiles, who do not possess the law, do instinctively what the law requires, these, though not having the law, are a law to themselves.
15 They show that what the law requires is written on their hearts, to which their own conscience also bears witness; and their conflicting thoughts will accuse or perhaps excuse them
16 on the day when, according to my gospel, God, through Jesus Christ, will judge the secret thoughts of all.