Fellowship In The Truth

See "A Plea For Unity--Based on Soundness" in the "Online literature" section for an excellent synopsis of this subject

"Declare what you as a body believe to be the apostles' doctrines.  Invite fellowship upon that basis alone.  If upon that declaration, any take the bread and wine, not being offered by you, they do so upon their own responsibility, not on yours.  If they help themselves to the elements, they endorse your declaration of doctrine, and eat condemnation to themselves."  Bro. Thomas,  The Christadelphian Vol. 7, 1870, Pg 16

"Is a brother walking disorderly in associating in fellowship with Methodists?  He would say 'yes.'  Upon the very same principle we say that a brother is walking disorderly who fellowships those who deny the scriptural doctrine of resurrection, and teach and believe another; and who, deny THE judgment; and either teach another or no judgment at all.  The one who fellowships such, fellowships with heretics, thereby walks disorderly, and becomes unfit for fellowship with those who desire to hold the truth in its purity."  Bro. Williams, The Advocate Vol. 2, 1886, Pg. 64

"We do not advocate any ultra strict or tyrannous action on the part of any ecclesia, but we do hold that there is ample apostolic warrant for withdrawal when any elements of the Truth are subverted, or when those professing the name of Christ are "factious" and are not susceptible to scriptural entreaty and forbearance.

To deny this is to pave the way for such a gradual mixture of truth and error as will wipe out the scriptural line of demarcation between the two.  For error is so insidious that, although its beginning be small, it will, sooner or later, act like a canker by eating the vitality out of Divine Truth."  Bro. J. J. Andrew, The Sanctuary Keeper Vol. 7, 1901, Pg. 92 

"'He that biddeth him God speed is partaker of his evil deeds.'  This applies to all without distinction, and erects a barrier to fellowship with even some who hold the truth;  for though they may hold the doctrine of Christ themselves, yet, if they keep up a 'God-speed' connection with those who do not, by John's rule they make themselves partakers with them, and, therefore, cut themselves off from those who stand for the doctrine of Christ." Bro. Roberts, Seasons of Comfort Vol. 1, Pg. 127, 'Love and Doctrine'  
"Chicago, Ill.--Brother W. A. Harris says 'We have thought it necessary to adopt the rule adopted in England and elsewhere, that when a stranger visits us, he be required to produce a letter of recommendation before we receive him into our fellowship;  failing which, we appoint a committee to confer with him as to the identity of his faith and practice with ours.  Please state this in the Christadelphian for the information of the brethren."--Intelligence from The Christadelphian Vol. 10, 1873, Pg. 47  
"We have been giving a few lectures in Mumbles, our old home, where we have been taking a good rest, also, by invitation, in Porth, and have visited Aberdare; but so far we have not been able to break bread with these ecclesias, not because they are unsound on the question of inspiration, or free life, or immortal emergence, or any of the false doctrines which have been allowed to be taught among those represented by the Visitor; but because they have been in fellowship with that body."  Bro. Williams;  The Christadelphian Advocate; Vol. 23 1907 Pg. 344  
"Now I beseech you, brethren, by the name of our Lord Jesus Christ, that ye all speak the same thing, and that there be no divisions among you; but that ye be perfectly joined together in the same mind and in the same judgment."  Paul;  1 Corinthians 1:10

“The message to the seven ecclesias was addressed directly to the Star-Angel, or the eldership, (as Dr. Thomas termed it) and they were not accused of holding the false teachings that were in their ecclesia personally, but they said because ye have those that believe these things.  So it’s vitally important that an ecclesia not allow these things to exist in their membership.  And they cannot feel—the people in an ecclesia cannot feel that it’s alright if they keep their own skirts clean, and allow others in their ecclesia to believe or practice wrong doctrine or conduct.  Then Christ would say what he said to those ecclesias, “I have somewhat against you,” if we allow this to happen.”—Bro. L. E. Parker; 2520 Years of Fulfilled Prophecy Class 2 at approx. 26:05