Thomas Boston, Works, 2:73:
The law is perfect, and requires a full conformity thereto. It requires the utmost perfection in every duty, and forbids the least degree of every sin. So that life and salvation are absolutely unattainable by it, since no man can perform such an obedience to it as it requires. Our salvation is suspended in obedience to the law; which since we cannot perform, let us be induced to betake ourselves to the obedience and satisfaction of Christ, by which the law is magnified and made honourable, and with which God is well pleased; and will be pleased with every sinner that takes the benefit thereof.