“Luther likens faith to ‘butter in the sunshine.’ While Luther will always maintain that trust in the promise makes baptism efficacious, he is wary of focusing on faith: ‘One must believe, but we neither should nor can know it for certain.’ Therefore, one dare not base his baptism on his faith.  For who can be sure if he really believes? The enthusiasts’ stress on subjectivity, like the late medieval view of penance and monasticism, troubles Luther because it puts the question of salvation back into the hands of a frail and doubting humanity. God, however, is merciful. He comes to us via outward means-water, bread, and wine. He pledges himself to us in these visible and tangible signs, for ‘faith must have something to believe something to which it may cling and upon which it may stand.’”

Mark Tranvik, “Luther on Baptism”  Lutheran Quarterly (Spring 1999),