How come the early church spread so fast? What made Christianity take off like wildfire?
The Birth of the Church
Pentecost essentially marks the birth of the church that Jesus Christ built. Jesus said that the gates of hell would not prevail against the church (Matt 16:18) meaning that not even death itself or the gates of hell (death) would not stop the church because He is God and you cannot stop the purposes of God. Even Saul (later became Paul), who was the mightiest persecutor of the church, could not possibly stop the church from growing (Acts 9:3-9. The church grew rapidly in the beginning. How was it able to grow so fast? Acts 2:42-47 shows just how this happened:
“And they devoted themselves to the apostles’ teaching and the fellowship, to the breaking of bread and the prayers. And awe came upon every soul, and many wonders and signs were being done through the apostles. And all who believed were together and had all things in common. And they were selling their possessions and belongings and distributing the proceeds to all, as any had need. And day by day, attending the temple together and breaking bread in their homes, they received their food with glad and generous hearts, praising God and having favor with all the people. And the Lord added to their number day by day those who were being saved.”
Devotion to Biblical Teaching
Notice some very key points in these verses about the reason the church grew so quickly. They devoted themselves to the apostles teachings. They were taught by the disciples and then they devoted themselves to doing what they were taught. These were no “pew potatoes.”
Devotion to Fellowship
Next, they were also devoted to one another in the fellowship. To have relationship we need to have fellowship with the saints which is why it is next to impossible for so-called “lone ranger” Christians to grow in the grace and knowledge. The Greek word for fellowship is “koinonia” which means their fellowship created a “mutual bond” which overrode each individual’s pride. Koninia is more than just fellowship; it is a family-type relationship and commonality.
The early church was also devoted to the “breaking of bread” which could mean frequent communion or it could mean that they just loved spending time with one another and often ate together. I once heard a pastor say that a church could grow closer together if they only worked together, played together, and ate together. I believe that is true.
Devotion to Prayer
Next, the early church devoted themselves to prayer. What more important thing could the early church be doing than praying? Much of what we pray for might be centered on ourselves but it seems that the early church prayed for the lost, the safety of the apostles, for the growth of the church, and for a bold witness of the gospel of Jesus Christ.
The church also had “all things in common” because they were all very likely being persecuted together. They even “sold their possessions and belongings and [were] distributing the proceeds to all, as any had need.” It’s amazing how generous these believers were. They sold their possessions and their belongings just so they could distribute the proceeds (the money) to all…that’s all! And they did this to “any [who] had need.”
Praising God Together
Finally, they were “praising God” because He is worthy. That is the purpose of church; to glorify God and to praise Him. When we praise God, even in persecution, God will bless that person who praises Him even in the storms of life.
Blood of the Martyrs
One way the church spread so rapidly in the first century was because of persecution. Ironically, the more the church was persecuted, the quicker the church grew. One example was in Acts 8:1-4 where Saul was going about killing and imprisoning Christians, but what was the result? Luke writes, “And there arose on that day a great persecution against the church in Jerusalem, and they were all scattered throughout the regions of Judea and Samaria, except the apostles. Devout men buried Stephen and made great lamentation over him. But Saul was ravaging the church, and entering house after house, he dragged off men and women and committed them to prison. Now those who were scattered went about preaching the word.” Notice that when the church was persecuted, they “were scattered [and] went about preaching the word.” The only thing that persecution of the church managed to do was to spread the church into other parts of the Roman Empire. Like a person trying to stomp out a grass fire, he only manages to spread it.
The 2nd-century church father Tertullian was right when he wrote that “the blood of the martyrs is the seed of the church.” The more the church was persecuted, the more she spread. To make martyrs  of Christians does nothing more than to spread the message of the gospel. The publicity of these martyrs deaths and the gruesome ways in which they died, help many in the Roman Empire take note of just how peacefully they died. Many sang hymns while they died. During the Middle Ages when the Black Plague hit, the funerals of the believers were so much more joyful than those who were not Christians. This attracted a great deal of attention in the way that these peculiar people died. They lived so well that people began to have hope in God and this opened up the door for the gospel to be presented…they died so well that they started to believe that they were going to a much better place.
The church grew, and can grow today, by following in the footsteps of the early church. If a church wants to grow and if Christianity is to spread, believers must devote themselves to their pastor’s or leader’s teachings, they must be devoted to one another in the fellowship  of the saints, they need to spend time breaking bread (or eating) together which required spending time with one another, they need to be devoted to ongoing, continual prayer, they need to be sharing with one another and giving away or being generous with those who have needs, and finally they must be praising our generous and gracious God. He is better to us than we deserve. There are fewer ways to grow Christianity today than to follow what the apostles taught (the Bible), spending time together with other Christians, eating together, being prayer warriors, helping those who have little, and praising the God for all that He has done for His children. What might happen if this occurs? Acts 2:47 tells us: “And the Lord added to their number day by day those who were being saved.” I say amen  to that. How about you?
Related reading: Praying for Those That Persecute Us 
Resources: New International Version Bible (NIV) THE HOLY BIBLE, NEW INTERNATIONAL VERSION®, NIV® Copyright © 1973, 1978, 1984, 2011 by Biblica, Inc.™ Used by permission. All rights reserved worldwide