The night of His arrest, Jesus offered this supplication to His Father:
"I do not ask on behalf of these alone, but for those also who believe in Me through their word; that they may all be one; even as You, Father, are in Me and I in You, that they also may be in Us, so that the world may believe that You sent Me. The glory which You have given Me I have given to them, that they may be one, just as We are one; I in them and You in Me, that they may be perfected in unity, so that the world may know that You sent Me, and loved them, even as You have loved Me." --John 17:20-23
Our Lord prayed not only for his immediate disciples, but also those who would believe in Him through their word. That, by extension, applies to us. That we would be "one", perfected in unity as was He and the Father. Upon seeing this unity, the world may come to realize that Jesus was indeed the Christ, the anointed one of God.
That prayer was initially answered the day of Pentecost, when some three thousand souls came to believe as a result of the apostle's teaching. Through the work of the Holy Spirit in their midst, and the unity of the new believers, others came to believe in Jesus day after day:
"So then, those who had received his word were baptized; and that day there were added about three thousand souls. They were continually devoting themselves to the apostles' teaching and to fellowship, to the breaking of bread and to prayer. Everyone kept feeling a sense of awe; and many wonders and signs were taking place through the apostles. And all those who had believed were together and had all things in common; and they began selling their property and possessions and were sharing them with all, as anyone might have need. Day by day continuing with one mind in the temple, and breaking bread from house to house, they were taking their meals together with gladness and sincerity of heart, praising God and having favor with all the people. And the Lord was adding to their number day by day those who were being saved." --Acts 2:41-47
A few chapters later, we read:
"At the hands of the apostles many signs and wonders were taking place among the people; and they were all with one accord in Solomon's portico. But none of the rest dared to associate with them; however, the people held them in high esteem. And all the more believers in the Lord, multitudes of men and women, were constantly added to their number." --Acts 5:12-14
Over time, breaches in that unity occurred, as seen in Paul's address to the Corinthians:
"...I have been informed concerning you, my brethren, by Chloe's people, that there are quarrels among you. Now I mean this, that each one of you is saying, "I am of Paul," and "I of Apollos," and "I of Cephas," and "I of Christ." Has Christ been divided?..." --1 Corinthians 1:11-13
Paul acknowledges their tendency toward division and reveals unrepentant sin as the cause:
"...in the first place, when you come together as a church, I hear that divisions exist among you; and in part I believe it. For there must also be factions among you, so that those who are approved may become evident among you." --11:18-19
The cure? Repent and prevent!
"Now I exhort you, brethren, by the name of our Lord Jesus Christ, that you all agree and that there be no divisions among you, but that you be made complete in the same mind and in the same judgment." --1:10
"Therefore I, the prisoner of the Lord, implore you to walk in a manner worthy of the calling with which you have been called, with all humility and gentleness, with patience, showing tolerance for one another in love, being diligent to preserve the unity of the Spirit in the bond of peace. There is one body and one Spirit, just as also you were called in one hope of your calling; one Lord, one faith, one baptism, one God and Father of all who is over all and through all and in all."
--Ephesians 4:1-6
And let us not forget these words by Paul:
"If anyone thinks he is a prophet or spiritual, let him recognize that the things which I write to you are the Lord's commandment. But if anyone does not recognize this, he is not recognized." --1 Corinthians 14:37-38
Remember, the world is watching, and can recognize division for what it is, as seen even in its own dictionaries:
division - n. 1.a. The act or process of dividing. b. The state of having been divided. 2. The proportional distribution of a quantity or entity. 3. Something, such as a boundary or partition, that serves to divide or keep separate.... 9.a. Variance of opinion; disagreement. b. A splitting into factions; disunion. denominationalism -n. 1. The tendency to separate into religious denominations. 2. Advocacy of separation into religious denominations. 3. Strict adherence to a denomination; sectarianism. --The American Heritage Dict.
In Paul's time, the church was considered to be in a state of sin if it became complacent toward division.
Is this not true today?
Is it not time to repent and prevent?