In Matthew 16:13-19, Jesus, upon hearing Simon Peter's confession that He is the Christ, the Son of the living God, declares that He will build His church on this rock, affirming that the gates of Hades shall not prevail against it. He further grants Peter the keys of the kingdom of heaven, with the authority to bind and loose on earth, which will be reflected in heaven. This moment marks a foundational step, as Jesus indicates His intention to establish His church following Peter's recognition of His divine identity. On the Day of Pentecost in AD 31, as recorded in Acts 2:1-4 and 2:14-41, the church is visibly founded with the outpouring of the Holy Spirit. A mighty wind fills the house where the disciples are gathered, and tongues of fire appear upon each of them. They are filled with the Holy Spirit and begin to speak in other tongues, demonstrating the Spirit's power. Peter addresses the crowd, explaining this event as the fulfillment of Joel's prophecy, proclaiming Jesus as both Lord and Christ, raised from the dead by God. This powerful message leads to the conversion of about three thousand souls, who are baptized and added to the church that day, showcasing the immediate fruit of the Spirit's work. Despite later corruption within generations, as seen in historical shifts by the second century, Jesus' promise holds that His church will endure against the powers of death and the schemes of satan the devil. The church, though challenged by external and internal corruption, continues through the faithful who often went underground to remote areas to practice their faith, ensuring its persistence as Jesus founded it. The feast of Pentecost serves as an annual reminder of this founding and the giving of the Holy Spirit, which empowers the church to fulfill its purpose.

When Jesus founded the church of God on the Pentecost after His death, resurrection, and ascension to heaven, it was a unified church. That unified church spread from Jerusalem into Judea and then into Samaria and then to the ends of the earth. For many years it was expanded and held together through the cooperation of the apostles despite their far-flung missions. It remained a singular church. On that day the 120 disciples were all with one accord in one place when they received the Holy Spirit and began to speak with other tongues. After Peter's sermon about three thousand souls were added, and the new believers continued steadfastly in the apostles' doctrine and fellowship, breaking bread and praying. They continued daily with one accord in the temple and from house to house, eating with gladness and simplicity of heart while praising God. The Lord added to the church daily those who were being saved. The foundational chapter on the church is framed by this repeated emphasis on unity, beginning and ending with the disciples in one accord. God does not construct His Word without purpose. The repeated phrase and the internal examples show His desire for accord, harmony, and unity among His people. This oneness was produced by a lavish outpouring of the Holy Spirit that overcame ethnic, cultural, linguistic, and social differences, molding diverse individuals into a unified whole. It fulfilled Joel's prophecy and served as a sign of the last days. The founding therefore established the pattern that the church is God's spiritual organism, organized for feeding on spiritual food, training and developing spiritual righteous character in those who will form the firstfruits at the resurrection. Its dual responsibility is to proclaim the gospel of the coming Kingdom and to feed the sheep. The church is a necessary instrumentality preparatory to bringing salvation to humanity, not merely to save those called but to prepare them as instruments for the greater salvation of all mankind.

The founding of the Church occurred on the Day of Pentecost in 31 AD when the promised Comforter, the Holy Spirit, first came upon the disciples as the initial outpouring of God's Spirit upon the New Testament firstfruits. This event marked the beginning of the Church era, fulfilling the timing established by the Feast of Firstfruits fifty days after the Days of Unleavened Bread. The disciples had been instructed to remain in Jerusalem and wait until they received power from on high, and the Spirit arrived suddenly with a sound like a rushing mighty wind that filled the house, accompanied by divided tongues as of fire resting on each person. All present were filled with the Holy Spirit and began speaking in other languages as the Spirit gave them utterance, with the miracle extending also to the hearing so that each listener understood in his own native tongue. These manifestations were unique to this one-time advent and served to draw attention to the arrival of the Spirit, which had not been given previously because Jesus had not yet been glorified. The teaching that followed emphasized repentance and baptism in the name of Jesus Christ for the remission of sins as the conditions for receiving the gift of the Holy Spirit, with no requirement for tarrying, persistent pleading, or repeated phrases. Three thousand responded that day and were added to the Church. Subsequent instances of the Spirit's reception, such as in Samaria, at Cornelius's house, and in Ephesus, occurred through the same conditions of repentance and faith without repeating the original manifestations, confirming that the baptism with the Holy Spirit is the immersion into the one body of Christ by means of the Spirit and is identical to receiving and being filled with the Holy Spirit.