No, it is very Biblical and comes from the mouth of Christ himself:
"My sheep hear my voice, and I know them, and they follow me"
If we are his sheep, and we follow him, and he knows us, then clearly we are members of his ekklesia - the called out assembly.
Sure, but in the same place he also speaks of the wolves that are capable of scattering the sheep, how he has other sheep who do not belong to the fold that he must call into the fold so that there is one flock and one shepherd, etc. And, if the parable of the lost sheep is to be believed, sheep can often enough do their own thing. I agreed that the imagery being used was biblical, but I rejected that the teaching itself (or your understanding thereof) was biblical.
It's too simplistic to believe that everyone who "follows Christ" is part of an amorphous thing called the Church. Which Christ? There are many Jesuses (Jesii?) being preached out there. Before the NT was written, Christ was only prefigured in the OT...it was the Church who made him known, and from which the NT flowed. And that was a distinct body. I'm not saying that the Upper Room of Acts 2 had a sign on it saying "St Mark's Syrian Orthodox Church" or anything like that (though now it does
), but it was still a distinct body with a distinct leadership, succession, membership, etc. In the passage where a man is casting out demons in Christ's name, and the apostles ask Jesus if they should stop him since "he's not one of us", he doesn't deny that he's not "one of us", even if he tells them not to stop him because whoever does good works in his name will not easily speak evil of him...they may be allies in some sense, but they're still not "one of us". Being Jesus' BFF isn't enough.
and that He might reconcile them both to God in one body through the cross, thereby putting to death the enmity.
that the Gentiles should be fellow heirs, of the same body, and partakers of His promise in Christ through the gospel,
We are quite off topic though, I just wanted to clarify Luther's position since it was brought up by another poster.
"One body" or "same body" only mean what you think they mean here if you take Luther's presupposition. If you read Eph 2 and 3 in context, it's talking about how the Gentiles who were alienated from Israel have been brought near, incorporated into one body with the (believing) Jews, through Christ. Israel was not some "YHWH fan club", it was a distinct body with a distinct leadership, succession, membership, etc. That doesn't just disappear into an amorphous blob when Christ comes along, but he reveals what that distinct body foreshadowed. Israel is God's firstborn son, according to the prophets...it's an icon of Christ's body, the Church. In the dispensation of Christ, it doesn't transform into a cloud or a ghost, but remains a concrete reality, as Christ's own human flesh was. When St Ignatius of Antioch writes about certain schismatics who rejected the Eucharist, he uses this sort of incarnational argument: they reject the Eucharist because they reject Christ's incarnation, but if they celebrate it, they must believe that he took flesh, and so have no excuse for separating themselves from the visible Church.
I appreciate that you were just trying to clarify a point and not trying to sidetrack the discussion; I don't want to do that either. My issue is with Luther. I don't think that identifying and defining the Church as the NT does--as a visible, concrete body--and identifying that body in history with the Orthodox Church necessarily excludes a lot of great charitable Christians or puts limits on God. It doesn't do that anymore than your assertion that Christian faith and baptism are necessary. God can and will save whomever he wants, but he does that through Christ's body, both in terms of the paschal mystery and in terms of the (visible) Church. "The saved" are connected in some way to that body, whether we are aware of it or not, whether it takes the form of a faithfully lived Christian life as a regular member of Ss Anargyroi on Fifth St or in some seemingly unconnected way. But just as you say that Christian faith and baptism are necessary according to the Scriptures, we would argue the same: we know what God has revealed to us, we know that "this way" works, and so while we can hope optimistically for others' sake, that doesn't absolve us of the responsibility of proclaiming the gospel and inviting people to become members of Christ's body. Salvation is God's business, and he can figure it out, but we know what he wills for man, what he has revealed to us as necessary, and that includes the visible (Orthodox) Church.