On the Hebrew Shavuot or Greek Pentekosté the Jews commemorated the descent of God’s Law on Mount Sinai, wreathed in fire, 50 days after the Exodus. Fifty days after Our Lord’s Resurrection, and 10 days after His Ascension (10 symbolising perfection), the fiery Holy Spirit descended on the Apostles and first disciples to breathe life into Christ’s new Body, new Temple, our Church. This magnificent Sunday (which in the Roman Rite’s Extraordinary Form retains its Octave – absurdly abandoned in the Novus Ordo – along with the special Communicantes and Hanc igitur) has in the Ordinary Form a Collect rooted in the ancient Gelasian Sacramentary: