"Confident" that you are "Christ's"
Imagine, a child acting as if his or her sibling was not part of the family - ignoring, not talking to, avoiding the other...and etc. That would be cruel, and unacceptable. And that is what was happening in the church at Corinth.
Paul was put down by "these super-apostles", in the eyes of the Corinthian believers. "These super-apostles", false teachers, had the charisma, health, wealth and were probably great speakers, but of the apostle Paul, the word on the block was - "...they say, “His letters are weighty and strong, but his bodily presence is weak, and his speech of no account.” And on top of that, if Paul was an apostle of the Lord, why did he have so many weaknesses, sufferings, insults, hardships, persecutions, and calamities? Plainly put, he has been rejected by many, and as it seemed to others, even by God himself!
But, what was the truth? Listen to what the apostle Paul says to the Corinthians, "Look at what is before your eyes. If anyone is confident that he is Christ's, let him remind himself that just as he is Christ's, so also are we." (2 Corinthians 10:7)
It is a great and important thing to be "confident" that you know you are "Christ's". But what is it that makes one so important in his own eyes, that he or she rejects another, as not belonging to God, to Christ? It is the octopus of many sided PRIDE! Many sided expression of selfish self. Pride has killed many. And the answer to this problem is not more self-control, but a total denial of self. “If anyone would come after me, let him deny himself and take up his cross daily and follow me." (Luke 9:23) My favorite author H.C.G.Moule says, "to deny" much more resembles in idea "to ignore" than "to control".
Listen to Paul again, "Look at what is before your eyes." He was saying to them to look at the evidence of the truth of Christ, in his life - his love for God, his word, love as a father for the Corinthian church, and all other churches. The evidence was clear. He was not like the "super-apostles", using the Corinthian believers. His faith was genuine.
You and I, we, must open our minds and hearts to others, and see that not all believers in Christ will be like us, and remind ourselves that just as I am "Christ's", so also is he, she, and we all. "Look at what is before your eyes". So, brother and sister, may you "Never look down on anybody unless you're helping them up." (Jesse Jackson) And may we who love God, remind one another that we are Christ's. God doesn't expect us to prove ourselves to him, so, shouldn't we expect that of each other.
If we love him, God accepts us with all our troubles, perplexities, and uniqueness of our difficulties. So must we, accept one another, in Christ, and realize we are all Christ's, because he has purchased us, by his blood.
"Therefore welcome one another as Christ has welcomed you, for the glory of God." (Romans 15:7)