The following is a quote from The Sum of Saving Knowledge, Section II by the Westminster Assembly

That the righteousness of every true Christian must be more than the righteousness of the scribes and Pharisees; for the scribes and Pharisees, albeit they took great pains to discharge sundry duties of the law, yet they cut short the exposition thereof, that it might the less condemn their practice; they studied the outward part of the duty, but neglected the inward and spiritual part; they discharged some of the meaner [lesser] duties carefully, but neglected judgment, mercy, and the love of God: in a word they went about to establish their own righteousness, and rejected the righteousness of God by faith in Jesus

But a true Christian must have more than all of this; he must acknowledge the full extent of the spiritual meaning of the law, and have a respect to all the commandments, and labor to cleanse himself from all filthiness of flesh and spirit, and “not lay weight upon what service he has done, or shall do,” but cloth himself with the imputed righteousness of Christ, which only can hide his nakedness or else he cannot be saved; so says the text [Matthew 5:16-20].