Is it right to take communion/Lord‘s supper even if someone is in sin or have unconfessed sin or hidden sin?
The Bible does not give a hard and fast command with regard to taking the Lord’s supper if one has unconfessed or hidden sin. Are you asking about sin which is unconfessed to and hidden from God or to/from other people? This would affect my answer. I do not believe we can hide sin from God and if we were aware of our sin against God before we took the Lord’s Supper, then I suppose that would amount to confessing it. So…. I will assume that you are talking about hidden or unconfessed sin which is unconfessed to and hidden from people.
1 Corinthians 11:27-32 has been used by some to teach that if we are “in sin” we should not take the Lord’s Supper. I do not see that taught in this passage. Here, Paul does not suggest people not take the bread and wine, he suggests that they should examine themselves. We should examine ourselves and then take the bread and the cup. That is the advice in this passage. There is no mention of or even suggestion of not taking the bread and wine. In any case, he is talking about “judging ourselves.” He is certainly not talking about confessing to another person.
Now, I would certainly agree that if we have unconfessed and hidden sin, then we ought to confess and come into the light (James 5:13-16), but what I do not see taught is that if we are in sin we should not take the Lord’s Supper.
I have also seen Matthew 5:21-24 used to teach that if we are in sin against a fellow Christian we should not take the Lord’s Supper until we make it right. Again, that certainly is not what is taught in Matthew 5:21-24. This passage is talking about bringing a gift or sacrifice to God, not about remembering the death of Jesus. The Lord’s Supper is not a gift or sacrifice (despite false teaching on that by the Roman Catholic Church), it is a remembrance and a time to reflect.
But, as above, I agree with the suggestion that if we have a problem with our brother, we should take care of that as our highest priority–even putting it ahead of works of service to God and the church, but I simply do not see the teaching that we should not take the Lord’s Supper if we have a problem with our brother.
Now, I believe that if it is the personal conviction on the heart of a particular individual Christian that they want to hold off on taking the Lord’s Supper because of a sin they are trying to repent of or because of a relationship they need to heal, I would not be opposed to that, but this should not be taught as a doctrine and, personally, I believe that this is not a particularly good way to help deal with the situation. We should continue to take the Lord’s Supper and use it as it is at least partially intended, which is as a chance to judge ourselves and come to conviction about taking care of such things. How holding back from the remembrance would help to deal with sin is not clear to me, but if that helps someone, I cannot think of a reason to speak against this practice.
I hope this helps.