Pentecost is the feast that celebrates the descent of the Holy Ghost on the apostles. After that, the apostles spread over the world to preach the Gospel.
According to some, Mary was also present.
Related works of art:
Dürer, Albrecht: The Descent of the Holy Spirit (1510)
El Greco: Pentecost (c. 1600)
Fouquet, Jean: The Apostles Receive their Mission (1452-60)
Fouquet, Jean: The Appearance of the Holy Spirit (1452-60)
Fouquet, Jean: The Descent of the Holy Spirit (1452-60)
Giotto: Pentecost (London) (c. 1310-1318)
Giotto: Pentecost (Padua) (1304-1306)
Lucas van Leyden: The Descent of the Holy Spirit (1530)
Van Dyck, Anthony: The Descent of the Holy Spirit (1618-1620)