For everyone to be admitted to the Lord’s Supper, without distinction or selection, is a sign of contempt that the Lord cannot endure. The Lord himself distributed the supper to his disciples only. Therefore anyone not instructed in the doctrine of the gospel ought not to approach what the Lord has instituted. No one should be distressed when his Christianity is examined even down to the finest point when he is to be admitted to the Lord’s Supper. It should be established as part of the total state and system of discipline that ought to flourish in the church that those who are judged unworthy should not be admitted.”
– John Calvin, “Letter on Various Subjects” in the book Calvin’s Ecclesiastical Advice. (from: http://www.puritandownloads.com/swrb/categories/Lord%27s-Supper-%28Communion%29/)
“I reckon them all as belonging together (that is, as Sacramentarians* and enthusiasts), for that is what they are who will not believe that the Lord’s bread in the Supper is his true, natural body, which the godless or Judas receive orally as well as St. Peter and all the saints. Whoever, I say, will not believe this, will please let me alone and expect no fellowship from me. This is final.”
*Martin Luther is referring to those who did not believe that the bread and wine are truly the Lord’s body and blood. This included those who followed the Swiss Reformer, Ulrich Zwingli.
“… lay people who refuse to learn (the catechism—ed.) should not be admitted to the Sacrament, and fathers must insist that children learn to recite these basics” – Martin Luther, Oxford Encyclopedia of the Reformation, Vol. 1, p. 276.
In January of 1533, the Lutheran congregation in Frankfurt, Germany received a letter from Luther in which he warned them against communing with those of another faith. He had in mind particularly the Zwinglian (Ulrich Zwingli, Swiss Reformer, 1484‐1531) deniers of the real presence of Christ’s body and blood in the Sacrament. You may think Luther’s language harsh by today’s standards. However, please consider the gist of his words and the important point they convey.
“It terrifies me to hear that in one and the same church or at one and the same altar both parties are to find and to receive one and the same Sacrament and one party is to believe that it receives nothing but bread and wine, while the other is to believe that it receives the true body and blood of Christ. And I often wonder whether it is credible that a preacher or shepherd of souls can be so hardened and malicious as to say nothing about this and let both parties go on in this way, receiving one and the same Sacrament, everyone according to his own faith, etc. If such a person exists, he must have a heart harder than any stone, steel, or adamant. He must, in fact, be an apostle of wrath. Whoever, therefore, has such preachers or suspects them to be such, let him be warned against them as against the devil incarnate himself.”
“Of all the [Church] fathers, as many as you can name, not one has ever spoken about the sacrament as these fanatics do. None of them uses such an expression as, ‘It is simply bread and wine,’ or, ‘Christ’s body and blood are not present.’ Yet since this subject is so frequently discussed by them [the Church Fathers], it is impossible that they should not at some time have let slip such an expression as, ‘It is simply bread,’ or, ‘Not that the body of Christ is physically present,’ or the like [if they had believed this], since they are greatly concerned not to mislead the people; actually, they simply proceed to speak as if no one doubted that Christ’s body and blood are present. Certainly among so many fathers and so many writings a negative argument should have turned up at least once, as happens in other articles; but actually they all stand uniformly and consistently on the affirmative side.” – Martin Luther.  That These Words of Christ, ‘This is My Body’ Still Stand Firm Against the Fanatics, 1527, in Luther’s Works, Word and Sacrament III, 1961, Fortress Press, ISBN 0800603370ISBN 9780800603373, volume 37, p. 54. (from: http://en.wikipedia.org/wiki/Sacramentarians).
The follow from W.J. McKnight, Pastor of the First Reformed Presbyterian Church Boston (RPCNA), Concerning Close Communion, 1930.
“An incident that happened a few years ago in my ministry might be cited in this connection, it seems to me, as an apt illustration. One of the ablest men I ever knew—the pastor of a neighboring congregation—accosted me on the street one day and said, ‘One thing about your Church I could never understand, that is, your position on Close Communion.’ In reply I said, ‘In point of principle our views on that question are the same as yours.’ ‘How is that?’ he said. ‘Suppose,’ said I, ‘that one of your members should strike a child down with an ax and kill it, would your Session allow him to go to the Lord’s table at the next communion?’ ‘Well,’ said he, ‘I should hope not.’ ‘Why?’ I asked. ‘Why, because he violated the Sixth Commandment,’ he said. ‘But,’ I protested, ‘he might hold that what he did was not murder.’ ‘Oh,’ said my friend, ‘we would not leave that to him; we would take that matter into our own hands.’ ‘You mean to say,’ I said, ‘that your Session would assume the responsibility of interpreting the Sixth Commandment and also of passing judgment on the man’s conduct, as to whether it was a violation of the Commandment thus interpreted.’ ‘Precisely,’ he said. ‘Well, then,’ said I, ‘why should you object to our Sessions when they do the same thing with respect to the First Commandment, and the Second, and the Third?’ ‘Oh, I see,’ he said, ‘and what is more I believe you are right; it never occurred to me in that light; with you Close Communion means that the Reformed Presbyterian Church intends to honor the Moral Law as the Church apprehends it, before anyone shall be permitted to take a seat at the Lord’s table under its jurisdiction and oversight.’ ‘Yes,’ said I, ‘that is the exact situation as we see it;’ and the man was satisfied. After all, to any person who really stops to consider, it is only a question of clear thinking and a sincere purpose to follow orders.”
Regarding Martin Luther:
However, although he disagreed with Rome over the mode of Christ’s presence, Luther did insist, over against Zwingli, that Christ was bodily, albeit invisibly, present in the bread and wine. Thus, in the Supper, ‘he is just as near to us physically as he was to [those who touched him during his earthly life].’ This being the case, Luther could maintain ‘both the physical and spiritual eating. The mouth eats the body of Christ physically.’ He did not, however, believe that physical eating is sufficient: faith is vital, otherwise ‘physical eating is…poisonous and deadly’, hence the importance for Luther of keeping Word and sacrament together, for faith comes by hearing the Word of God. (from: http://www.theologian.org.uk/doctrine/calvinonthelordssupper.html)