Moreover, they teach that every Christian ought to train and subdue himself with bodily restraints, or bodily exercises and labors that neither satiety nor slothfulness tempt him to sin, but not that we may merit grace or make satisfaction for sins by such exercises. And such external discipline ought to be urged at all times, not only on a few and set days. So Christ commands, 35] Luke 21:34: Take heed lest your hearts be overcharged with surfeiting; also Matt. 17:21: This kind goeth not out but by prayer and fasting. Paul also says, 1 Cor. 9:27: I keep under my body and bring it into subjection. Here he clearly shows that he was keeping under his body, not to merit forgiveness of sins by that discipline, but to have his body in subjection and fitted for spiritual things, and for the discharge of duty according to his calling. Therefore, we do not condemn fasting in itself, but the traditions which prescribe certain days and certain meats, with peril of conscience, as though such works were a necessary service.
Nevertheless, very many traditions are kept on our part, which conduce to good order in the Church, as the Order of Lessons in the Mass and the chief holy-days.
Augsburg Confession, 1530