Martin Luther — On the Babylonish Captivity of the Church — Of the Lord's Supper

“But why should not Christ be able to include His body within the substance of bread, as well as within the accidents? Fire and iron, two different substances, are so mingled in red-hot iron, that every part of it is both fire and iron. Why may not the glorious body of Christ much more be in every part of the substance of the bread?”