The most difficult aspect of the close(d) communion practice in our churches usually comes with the presence of a prospective communicant from another Lutheran denomination, especially the ELCA. Many people accept the fact that it is not appropriate for Catholics or Baptists to present themselves at our altar. But Lutherans from other denominations present a unique and thorny issue for the pastor. Where should the faithful pastor turn for support?
Exegetes readily admit that Paul's words in 1 Corinthians do not directly address denominational membership as we currently understand it. How could they? The church, thankfully, was yet one. Unfortunately the temptation exists to brush away our need for faithful fellowship at the altar by utilizing the seeming silence of scripture as our escape clause. Furthermore, it is argued that membership in a congregation that happens to belong to another denomination does not automatically imply that the prospective communicant possesses the confession of that church body. To a degree there is truth here. We do not deny the reality of 'felicitous inconsistency' where many a Lutheran possesses an orthodox understanding of the faith while belonging to a heterodox church body.
However, do we simply overlook this and disregard their denominational affiliation? No. Pastoral care exceptions aside, the public participation of a Christian in a congregation with which they hold formal membership does involve them, even unwittingly, in the errors of that church. And to what scripture do we appeal? My suggestion is that 1 Corinthians 10:14-22 is our firmest ground in this case. Now I can already hear the protests since Paul here is talking directly about those who participate in pagan rituals and worship while at the same time presenting themselves at the Lord's Table. Are you saying that the ELCA churches are demonic altars? No. My point here is that Paul clearly shows how the involvement of a person in the sacrificial worship of any religion is a real participation (communion) in that faith.
I make this first point because the argument is often put forth that a person's involvement or association with the ELCA does not connect them in any way with the errors of that church. To the contrary, participating in a church that teaches error connects you intimately with those errors whether you intend it or not. Thus, when talking about error and falsehood in the church as much as the demonic deceptions of the pagans, Paul's instructions are clear: flee! One could imagine a Christian of the first century arguing with Paul trying to convince him that being at the pagan temple was just a social thing, and that he was in not danger of straying from his Christian faith. He could do both, no harm. Paul, however, would warn him that his confidence was overstated and the danger was real.
Furthermore, the issue of unity is also at stake. In the same context Paul states: "Because there is one bread, we the many are one body, for we all share in the one bread" (vs. 17). A careful examination of the first chapter of 1 Corinthians will reveal the divisiveness already present within the Corinthians congregation and Paul's call for unity. They are lining up in differing factions. They are embracing contrary teachings. All this is unacceptable. That unity is now further threatened by the careless participation of some of its members in the religious rites of the neighboring pagan temple.
When a person tries to maintain their participation in two churches that teach different doctrines and are not in unity of faith, is this really any different? In our individualistic culture today we loathe the idea that the actions of those with whom we might associate could be connected with us. We are 'free agents' accountable only to ourselves, and if we must, directly to God on our own terms. It is as if the church hardly exists in this cases; merely me and Jesus is all that counts.
We must hold people accountable for the confessions with which they associate themselves. If they don't believe what a given church teaches, then leave. You have a choice - and a responsibility! If you want to fellowship at my altar, then sever yourself from the demonic errors that you have become connected with, even if unintentionally. This is for the good of your own faith, not just the integrity of the church's public witness.