Is the carnal mind at enmity against God? Then salvation cannot be by merit; it must be by grace. If we are at enmity with God, what merit can we have? How can we deserve anything from the being we hate? Even if we were pure as Adam, we could not have any merit; for I do not think Adam had any desert before his Creator. When he had kept all his Master’s law he was but an unprofitable servant; he had done no more than he ought to have done; he had no surplus, no balance. But since we have become enemies, how much less can we hope to be saved by works! Oh! no; but the whole Bible tells us, from beginning to end, that salvation is not by the works of the law, but by the deeds of grace. Martin Luther declared that he constantly preached justification by faith alone, “because,” said he, “the people would forget it; so that I was obliged almost to knock my Bible against their heads, to send it into their hearts.” So it is true; we constantly forget that salvation is by grace alone.
From the Metropolitan Tabernacle Pulpit, Volume 1, Sermon 20 by Charles Haddon Spurgeon