Q: Is any man able perfectly to keep the commandments of God?
A: No mere man, since the fall, is able, in this life, perfectly to keep the commandments of God; but doth daily break them, in thought, word, and deed.

Q: Are all transgressions of the law equally heinous?
A: Some sins in themselves, and by reason of several aggravations, are more heinous in the sight of God than others.

(Questions LXXXII and LXXXIII from the Westminster Shorter Catechism.)