Romans 11:6

And if by grace, then it is no more of works — Whether ceremonial or moral. Else grace is no longer grace — The very nature of grace is lost. And if it be of works, then it is no more grace: else work is no longer work — But the very nature of it is destroyed. There is something so absolutely inconsistent between the being justified by grace, and the being justified by works, that, if you suppose either, you of necessity exclude the other. For what is given to works is the payment of a debt; whereas grace implies an unmerited favour. So that the same benefit cannot, in the very nature of things, be derived from both.