Romans 11:24

11:24 For if you were cut off from what is by nature a wild olive tree, and grafted, contrary to nature, into a cultivated olive tree, how much more will these natural branches be grafted back into their own olive tree?

Romans 11:21

11:21 For if God did not spare the natural branches, perhaps he will not spare you.

Romans 1:26

1:26 For this reason God gave them over to dishonorable passions. For their women exchanged the natural sexual relations for unnatural ones, ¹ 

¹ tn Grk “for their females exchanged the natural function for that which is contrary to nature.” The term χρῆσις (crhsi") has the force of “sexual relations” here (L&N 23.65).