Romans 2:14-15 NIV

14 (Indeed, when Gentiles, who do not have the law, do by nature things required by the law,1 they are a law for themselves, even though they do not have the law,

References for Romans 2:14

15 since they show that the requirements of the law are written on their hearts, their consciences also bearing witness, and their thoughts now accusing, now even defending them.)