Jesus inaugurated the church on Pentecost. The Catholic/Orthodox/Oriental Orthodox/Assyrian churches are that church, not your modernist interpretations like Mormons, Adventists, Pre-tribulation rapturists, Christian Scientists, Jehovah's witnesses etc
HE did?
HMMMmmm...
Acts 2:1-4 NIV
1 When the day of Pentecost came, they were all together in one place. 2 Suddenly a sound like the blowing of a violent wind came from heaven and filled the whole house where they were sitting. 3 They saw what seemed to be tongues of fire that separated and came to rest on each of them. 4 All of them were filled with the Holy Spirit and began to speak in other tongues as the Spirit enabled them.