Pentecost commemorates the descent of the Holy Spirit upon the apostles on the fiftieth day of Easter. This day was already a festival in the Jewish tradition, commemorating the giving of the law to Moses upon Mt. Sinai; the Apostles gathered to celebrate that festival, when the Holy Spirit descended upon them and moved them to speak in many languages. While the feast-day commemorates the historical event, it also asks for a descent of the Holy Spirit upon each believer present, and it does it in several ways. The second alleluia of the Mass includes the prayer "Come, Holy Spirit, fill the hearts of thy faithful; and kindle in them the fire of thy love." This is the only time in the year that at the alleluia verse the entire congregation kneels, awaiting, as it were, the gifts of the Holy Spirit. The sequence which follows elaborates upon that prayer, enumerating names of the Holy Spirit-Father of the poor, giver of gifts, light of hearts, best consoler, sweet refuge of the soul; and asks for the works of the Spirit-cleansing, moistening, healing, bending, warming, ruling, and ends by asking for the seven-fold gifts. The communion chant evokes particularly vividly the descent of the Holy Spirit, as described in the Acts of the Apostles, "Suddenly there came a sound from heaven as of a mighty wind coming," and it sings it to a melody that imitates the sound of a rushing wind.