Remaining elements of the Lord’s Supper
Is Christ's body and blood present in, with, and under the bread and wine that is not consumed but has been consecrated (leftover from the Lord's Supper)? Where in Scripture is the basis for the idea of some Lutherans that the extra consecrated bread and wine must be eaten or destroyed (poured in ground/burned) rather than put back with the yet to be used bread and wine? My understanding is consecration is "setting apart for a holy purpose," not a magical moment that makes the body and blood present; so is it really wrong to put it back rather than consume or destroy it?
Understanding what Scripture says about the Lord’s Supper led to this statement in one of our Lutheran Confessions: “To preserve this true Christian doctrine concerning the Holy Supper, and to avoid and abolish manifold idolatrous abuses and perversions of this testament, the following useful rule and standard has been derived from the words of institution: ‘Nothing has the nature of a sacrament apart from the use instituted by Christ’ or ‘apart from the action divinely instituted.’” (The Formula of Concord. Thorough Declaration. VII. Of the Holy Supper.)
The sacramental action in the Lord’s Supper is the consecration, distribution and reception of the bread and wine. The leftover elements stand apart from that sacramental action. That would allow for the storage and reuse of the unused wafers, and wine from individual cups and the flagon.
Because the unused elements were set aside for use in the celebration of the Lord’s Supper, people have taken different approaches—based on their thinking and guided by their consciences—on what to do with the bread and wine that was not distributed in the Lord’s Supper. Over the years practices have included consuming the leftover elements or disposing of the wine in a special sink that bypasses the regular wastewater system and instead deposits the wine on the ground outside the church. Other churches simply dispose of the leftover wine through a regular sink and drain.
Like many parts of church life and the Christian life in general, there is freedom in this area. Churches have freedom to develop and implement a practice of their choosing.