Ten days after the Ascension, fifty days after the Resurrection, the apostles — with Mary and the women — were gathered in the Upper Room on Mount Zion. Suddenly a sound from heaven like the rush of a violent wind filled the whole house. Tongues as of fire appeared and rested on each one of them. They were filled with the Holy Spirit and began to speak in other languages, as the Spirit gave them utterance.
Outside, the crowd of Jewish pilgrims gathered in Jerusalem for the feast of Pentecost — from Parthia, Media, Elam, Mesopotamia, Judea, Cappadocia, Pontus, Asia, Phrygia, Pamphylia, Egypt, Libya, Rome, Crete, Arabia — heard each one in his own native language: 'We hear them telling in our own tongues the mighty works of God.' Peter stood up and preached the first Christian sermon. Three thousand were baptised that day. The Church considers Pentecost its own birthday and the foundational reversal of the confusion of tongues at Babel. The traditional site of the Upper Room is on Mount Zion in Jerusalem, on what is now the Hall of David's Tomb.