It was the “baptism” of the Church, baptism in the Holy Spirit (cf. Acts 1:5). As the Acts of the Apostles recount, on the morning of the feast of Pentecost, a noise as of wind burst into the Upper Room and tongues of fire, as it were, came to rest upon each of the disciples (cf. Acts 2:2–3). St Gregory the Great commented: “Today, the Holy Spirit has came down upon the disciples with an unexpected sound and changed the minds of carnal beings within his love; and while he appeared externally in tongues