The glory of the gospel is that God has declared Christians to be rightly related to him in spite of their sin. But our greatest temptation and mistake is to try to smuggle character into his work of grace. How easily we fall into the trap of assuming that we can only remain justified so long as there are grounds in our character for justification. But Paul’s teaching is that nothing we do ever contributes to our justification.
--Sinclair Ferguson, Know Your Christian Life (IVP, 1981), p. 73 via C. J. Mahaney's Interview with Sinclair Ferguson at C.J.'s View from the Cheap Seats