Pastor, if the Eucharist isn't consumed at the end of the service, does it stop being the Body and Blood of Christ? Or, what is the teaching on this?
Perhaps it's helpful to think about it this way:
We have no record of Christ nor the apostles saying anything explicit about when exactly the Sacrament ceases to be a Sacrament. But we do have records of the institution, and we also have the OT background and NT commentary on it! So what we do know, is that we are to receive it and consume it. There really isn't any other way.
Now, we also understand that the Church is not divorced from history, and so we value tradition. But we hold that tradition must be governed by Scripture, which we know is apostolic. So we treat later commentary on the Sacrament exactly as that — commentary but not inspired.
I'd be glad to expand on this controversy, but in brief: (A) We receive the Sacrament as given to us in accordance with God's Word. That eliminates any need for speculation or doubt. (B) In the unlikely event that Sacrament
must be discarded (I don't think there are many scenarios where there is a must!), we are to treat it with the highest reverence. In the OT it meant burning the Passover Lamb, so many follow this ancient tradition.
So, I'm forced to give you a non-answer, because God's Word doesn't say when the elements stop being the body and blood of Christ. It only constrains them to the Sacrament, proper, which consists of three parts: (1) The blessing or consecration, (2) the distribution and receiving, and (3) the sacramental eating and drinking. Anything outside of this is beyond God's Word.
You can find our formal confession regarding this in The Formula of Concord: Solid Declaration, VII, The Eucharist. I'd recommend reading the whole thing but I think what you're looking for specifically is touched on in 14-15 and 83.
We've published it here:
luco.the-rejected-stone.com
Finally, I can add that it can perhaps be helpful to consider the words of Christ when He says
"... this is ...". I think most who have studied dogmatics and church history, even in different traditions, will recognise that there has been a lot of debate and reflection on these words. But a good insight from the controversy, I believe, is this:
The
"this" in the sentence is not strictly the bread and the wine, but the Sacrament, the Holy Mystery. So when Jesus is saying:
"Take, eat; this is My body", understanding it as
"Take, eat; this bread is My body" is not wrong, but not a full understanding. A better and richer understanding would be something like
"Take, eat; this thing, this mystery, is My body". That is, Jesus isn't giving us special bread and wine, but a Holy Mystery. So the point here is that we should be careful about divorcing the body and blood of our Lord from the Sacrament. It's best treated as one thing, one gift, one action. This is most certainly how the sacrificial system in the OT functioned, and because that is the foundation of the Eucharist, or in other words, the Eucharist is the culmination of the OT sacrificial system, it's good to treat it as such — with reverence and as one thing.
Hope this helps and I'd be glad to expand on any of this!