We should, therefore, regard membership in the orthodox Church not only as our duty, but also as the greatest privilege and highest honor, even when tile orthodox Church outwardly bears a very humble form.
This thesis is a simple conclusion from the foregoing. If God has commanded fellowship with the orthodox Church — and that is the case, as we have seen — then this fellowship is our duty, a duty under all circumstances, and a duty for every Christian. God has, under no circumstances, given us a dispensation from the First Commandment, and has said to no Christian: You, for yourself, may cultivate church fellowship with false teachers, as though they were your brethren in the faith. Rather, God simply says: “Avoid them,” that is, avoid all who “cause divisions and offenses contrary to the doctrine which ye have learned.” Rom. 16:17. Accordingly, whoever has church fellowship with the heterodox is disobedient to God.
But we should look upon fellowship with the orthodox Church not merely as a duty, in the sense that it would be a bitter must for us; simply because a true Christian, who has learned to know God as his dear and gracious Father, is happy when he knows that in a certain matter he is doing God’s will. When he does what God commands him, the Christian walks as in a paradise, asLuther says. Thus, as we have learned, only in the orthodox Church is God given the honor which He demands, and only there are sinners rightly served, so that they reach the final goal set for man, salvation. Therefore, we should look upon membership in the orthodox Church as a most glorious privilege, as a great proof of God’s grace, for which we can never sufficiently thank God. For we ourselves have not provided this treasure for ourselves, but it is the grace of God which has led us into this Church. Therefore we must, if we only reflect a bit, daily thank God on our knees, that we are members of the Church of the Reformation. Think of those Christians who are found within the heterodox Church. Compare our condition with theirs. Note how the souls of those who sincerely seek their salvation are hindered and tortured there, for example, by the false doctrine concerning the identification marks of a Christian, and by the false doctrine which makes the grace of God uncertain for sinners.
But now, even when a soul has found peace in the fact, that God, through His special grace, prevented error from getting a foothold and saw to it that the truth which was still preached in the heterodox Church was impressed upon the heart, there still remains something which must not be underestimated. Heterodox churches are such who cause divisions and offenses in Christendom. (Rom. 16:17.) Such Christians who are found in the heterodox churches support, without intending to do so, those evil works so strongly condemned in God’s Word. The heterodox churches, as such, are in a state of rebellion against God, because they will not follow certain parts of God’s Word. Now, those Christians who are in them strengthen, though unknowingly, this rebellion against God.
Finally: heterodox churches are in a continuous state of warfare against the orthodox Church, against that Church which, in conformity with the will of God, confesses all parts of the truth. Heterodox people revile and persecute those who abide by God’s Word. Surely, an evil work! For Christ says that He will regard that which is inflicted upon those who confess Him as being done to Him. Now, those Christians who are in heterodox churches take part in this evil work and persecute Christ in His confessors of the truth.
from Franz Pieper, ‘The Distinction Between Orthodox & Heterodox Churches’
HT: Gnesio Lutheran