FAITH: A LIVING, DARING CONFIDENCE
"Faith is a living, daring confidence in God’s grace, so sure and certain that the believer would stake his life on it a thousand times. This knowledge of and confidence in God’s grace makes men glad and bold and happy in dealing with God and with all creatures. And this is the work which the Holy Spirit performs in faith. Because of it, without compulsion, a person is ready and glad to do good to everyone, to serve everyone, to suffer everything, out of love and praise to God who has shown him this grace. Thus it is impossible to separate works from faith, quite as impossible as to separate heat and light from fire."
(Source: Luther’s Works, vol. 35, page 370)