The heart of man finds it difficult to believe that so great a treasure as the Holy Spirit is gotten by the mere hearing of faith. The hearer likes to reason like this: Forgiveness of sins, deliverance from death, the gift of the Holy Spirit, everlasting life are grand things. If you want to obtain these priceless benefits, you must engage in correspondingly great efforts. And the devil says, ‘Amen.’
We must learn that forgiveness of sins, Christ, and the Holy Spirit, are freely granted to us at the preaching of faith, in spite of our sinfulness. We are not to waste time thinking how unworthy we are of the blessings of God. We are to know that it pleased God to freely give us His unspeakable gifts. If He offers His gifts free of charge, why not take them? Why worry about our lack of worthiness? Why not accept gifts with joy and thanksgiving?
~ Martin Luther, Commentary on Galatians