What is Christianity?

Christianity did not begin as a new religion. It began as the fulfillment of God's ancient covenant with the people of Israel. To understand what Christianity truly is, we must trace the story from Abraham through the prophets, to Jesus the Messiah, and finally to the inclusion of the Gentiles into God's family.

This guidepost walks through the historical and theological journey: how the first believers were all Jews, how the gospel expanded to the Gentiles, and what it means that we who were once “far off” have been grafted into the olive tree of Israel through faith in Jesus the Messiah.

Christianity is fundamentally a sect of Judaism where Jesus is recognized as the Messiah — the “King of the Jews” who died to tear down the dividing wall and make both Jews and Gentiles one in Him.

On the day of Pentecost, after the Holy Spirit descended on the disciples, Peter stood up and preached to the crowd of Jewish pilgrims gathered in Jerusalem for the feast. His message was clear: Jesus of Nazareth, whom they had crucified, was both Lord and Messiah.

“Therefore let all the house of Israel know with certainty that God has made this Jesus, whom you crucified, both Lord and Messiah!”

The response was overwhelming:

“So those who accepted his message were baptized, and that day about three thousand people were added to them.”

These 3,000 were not Gentiles. They were “Jews, devout men from every nation under heaven” (Acts 2:5) — scattered Israelites who had returned to Jerusalem for the feast. The church began entirely within the Jewish people.

Yet even during His ministry to Israel, Jesus gave a glimpse of the grace that would later overflow to the Gentiles. A Canaanite (Gentile) woman came to Him, crying out for help because her daughter was demon-possessed.

“But he answered, 'I was sent only to the lost sheep of the house of Israel.' Yet she came and knelt before him, saying, 'Lord, help me!' He answered, 'It isn't right to take the children's bread and throw it to the dogs.' 'Yes, Lord,' she said, 'yet even the dogs eat the crumbs that fall from their masters' table.' Then Jesus replied to her, 'Woman, your faith is great. Let it be done for you as you want.' And her daughter was healed from that moment.”

Jesus' response tested her faith — and she passed. Her humility and persistence demonstrated that faith, not ethnicity, would ultimately be the mark of God's people. This was a foretaste of what was to come.

Before Jesus' death and resurrection, the Holy Spirit was given only to select individuals: the patriarchs (Abraham, Isaac, Jacob), the prophets (Moses, Elijah, Elisha), and the kings (Saul, David). The Spirit would come upon them for specific tasks, but could also depart.

But Jesus promised a new reality:

“And after saying this, he breathed on them and said, 'Receive the Holy Spirit.'”

After His resurrection, Jesus breathed the Holy Spirit on His disciples. Then at Pentecost, the Spirit was poured out on all believers:

“When the day of Pentecost had arrived, they were all together in one place. Suddenly a sound like that of a violent rushing wind came from heaven, and it filled the whole house where they were sitting. And tongues, like flames of fire that were divided, appeared to them and rested on each one of them. So they were all filled with the Holy Spirit.”

This was the fulfillment of Joel's prophecy: God would pour out His Spirit on ALL people — sons and daughters, young and old, male and female servants (Acts 2:17-18). The age of the Spirit had arrived.

The apostle Paul uses the metaphor of an olive tree to explain how Gentiles relate to Israel. The cultivated olive tree represents Israel — God's covenant people. The wild olive branches represent the Gentiles.

“Now if some of the branches were broken off, and you, though a wild olive branch, were grafted in among them and have come to share in the rich root of the olive tree, do not boast over the branches.”

Gentile believers did not replace Israel — they were grafted into Israel's covenant relationship with God. We do not support the root; the root supports us (Romans 11:18).

God's family structure is clear: the Hebrew people first, then everyone else grafted in through faith in the Jewish Messiah.