This Holy day of Obligation, 40th day of Easter, commemorates Christ’s Ascension into Heaven from Mount Olivet 40 days after He rose from the dead (Mark 16:14-20). After the Gospel is sung, the Paschal Candle, lit from the New Fire of the Easter Vigil, is extinguished to symbolize the departure of Christ (if you use a Paschal candle at home, it should be put away today, too).
The story of Our Lord’s Ascension and His foretelling of the Pentecost to come is recounted most fully by Luke in in Acts 1:1-11: