Yours is a very important, but controversial question.  I believe the scriptures are clear on this, so let us see what the Bible says. 

Let’s begin by reading 1 Corinthians 10:16, “The cup of blessing which we bless, is it not the communion of the blood of Christ? The bread which we break, is it not the communion of the body of Christ?”  The Greek word for ‘blessing’ in this verse is “eulogia”.  It’s where we get the word ‘eulogy.’  This word is also where we get the word ‘eucharist’ which is defined as: the Christian service, ceremony, or sacrament commemorating the Last Supper, in which bread and wine are consecrated and consumed.”  Now, let’s look at the word ‘communion’.  The Greek word is “koinonia” which means ‘fellowship.’  From this, we learn that we establish and acknowledge fellowship at the Lord’s Supper.  Most know this meal as the communion service. It is by partaking of the Lord’s Supper together that we show that we are in agreement with those who participate with us. 

How important is it to know that we are in agreement with those we remember the Lord with?  Amos 3:3 asks the searching question, “Can two walk together, except they be agreed?”  We cannot truly fellowship with those that we disagree with doctrinally.  The Lord will draw us together around Himself and His truths.  If we do not know what a person believes, we cannot have true fellowship with him.

Let’s consider 1 Timothy 5:22, “Lay hands suddenly on no man, neither be partaker of other men’s sins: keep thyself pure.”  What does this mean?  It means that we should not lay hands or accept someone into fellowship too quickly.  We should get to know a person before he is received as a part of our church group.  Is this person saved?  Are they walking in obedience to God’s Word?  Are they following the truths laid out so clearly in the scriptures?  The only way to make sure of these things is to spend time with that person, going over the truths found in the Bible to make sure we are on the ‘same page’ and that we agree on the essential truths concerning Christ…His person and His work. 

Twice, we are told that “a little leaven leaveneth the whole lump.”  (1 Corinthian 5:6 and Galatians 5:9).  Leaven is the same as yeast.  Most understand how that if we put yeast into an unbaked loaf of bread, it will permeate that whole loaf and cause the entire loaf to rise.  In the Bible, leaven is most often used as a type of sin, so these verses are telling us that if we allow sin (leaven) among us as a church group, that sin will penetrate the entire group and cause it to be impacted negatively.  1 Corinthian 5:6 speaks of the leaven of sinful behavior while Galatians 5:9 speaks of the leaven of false teachings.  Either one of those sins will have a negative impact on the group…and the group becomes guilty of the sin they allow among themselves.  Therefore, we need to take time to get to know someone…how they live and what they believe, before we welcome them to join us at the Lord’s Supper.

Let’s be clear, we should welcome any who come to us in order to be saved or in order to learn more about the Bible.  When we come to the place where we are walking together because we share the same truths and values, then we should heartily welcome that person to join with us in remembering the Lord as He has asked us to do.

In closing, I want to quote a Godly man and author, C.H. MacIntosh.  He wrote, “There are two things which should never be lost sight of in question of reception at the Lord’s supper, and these are, first the grace which will never not allow of the exclusion of any who ought to be admitted; secondly, the holiness which cannot allow the admission of any who ought to be excluded.”  Wise words for us to consider and use when considering the reception of someone to the Lord’s Supper.  (CC)  (540.6)