"Do not be fooled by people who say to you, 'You do not have to keep the law perfectly in order to be saved. You just have to be sincere. It is Jesus plus your own sincere obedience that will save you.' As attractive as those words might sound, do not accept them. They are a mask for a false gospel.
Second, remember the basic difference between the law and the gospel. It is not that the law requires perfect obedience, and the gospel just requires sincere obedience. Rather, the difference is this: the law requires doing, and the gospel requires not doing. The gospel requires believing for life and salvation. The 'terms of the deal' are totally different. They are not just different in degree: 'The law requires 100% obedience for your salvation whereas the gospel requires only 51% obedience for your salvation.' No! The terms are different in their very nature! The law requires 100% doing. The gospel requires 100% not doing. The gospel requires believing!"
- Walter Marshall, The Gospel Mystery of Sanctification, p. 82