Secondly, we must bear in mind how God purifies our hearts by faith. There is indeed a twofold purification: He first forms us in his image, and engraves on us true and real fear, and an obedient disposition. This purity of the heart diffuses itself over our works; for when we are imbued with true piety, we have no other object but to offer ourselves and all we have to God. Far indeed are they who are hypocrites and profane men from having this feeling; nay, they are wholly alienated from it: they offer liberally their own things to God, but they wish to be their own masters; for a hypocrite will never give up himself as a spiritual sacrifice to God. We hence see how faith purifies our hearts, and also purifies our works: for having been regenerated by the Spirit of God, we offer to him first ourselves and then all that we have. But as this purgation is never found complete in man, it is therefore necessary that there should come an aid from gratuitous acceptance. Our hearts then are purified by faith, because God imputes not to us that uncleanness which remains, and which defiles our works. As then God regards with gracious acceptance that purity which is not as yet perfect, so he causes that its contagion should not reach to our works. When Abel offered sacrifices to God, he was indeed perfect, inasmuch as there was nothing feigned or hypocritical in him: but he was a man, we know, encompassed with infirmity. It was therefore necessary for his remaining pollution to have been purified by the grace of Christ. Hence it was that his sacrifices were accepted: for as he was accepted, so God graciously received whatever proceeded from him.