(Related: 1, 2)
"If we doubt or do not believe that God is gracious and pleased with us, or if we presumptuously expect to please Him through our works, then all [our compliance with the law] is pure deception, outwardly honoring God, but inwardly setting up self as a false savior. Note for yourself, then, how far apart these two are: keeping the First Commandment with outward works only, and keeping it with inward [justifying faith]. For this last makes true, living children of God, the other only makes worse idolatry and the most mischievous hypocrites on earth..."