Sunday opened the Advent season, and Pope Francis used the occasion to remind Catholics to be aware at all times of Christ’s coming.

"Season of #Advent, let us be shaken out of our torpor to recognize God’s present in daily situations,” the pope tweeted this week. “If we are unaware of his coming today, we will also be unprepared when He arrives at the end of time. Let us remain vigilant!”

The readings on Sunday emphasized the need to stay ready and prepare for the coming of the Lord.

Bishop Robert Barron of the Diocese of Winona-Rochester posted a video on the first Sunday of Advent, calling it "the beginning of the liturgical year" and a "powerful spiritual season.” The bishop spoke about the "vigil quality" of the Christian life—of waiting and watching for the coming of the Lord. He also discussed the readings and how Catholics can bring their focus to the season of Advent.

The word “Advent” is derived from the Latin word meaning “coming,” a Crosswalk.com article said. Although Advent is typically thought of as a season of anticipating Christmas these days, it originated as a time when early Christians would prepare for the baptisms of new Christians on the Epiphany. The Advent season also anticipated the Magi visiting the baby Jesus, Jesus’ baptism in the Jordan River, and Jesus’ first miracle at the wedding in Cana. Christians used the Advent season as a weeks-long period of fasting and prayer. The season was not directly linked to Christ’s birth until the Middle Ages.

The first Sunday of Advent celebrates hope, Crosswalk said. Catholics pray and reflect on hope in God’s plan for deliverance through Christ.

On the first Sunday of Advent, Catholics light the first purple candle on their Advent wreaths, an article from the Daily Press said. The purple symbolizes preparation and repentance. The circular wreath symbolizes God’s eternal nature. The pink candle, which is lit on the third Sunday of Advent, signifies that the waiting period for Christ's birth is almost over.

“Brothers and sisters: You know the time; it is the hour now for you to awake from sleep,” the second of the USCCB Daily Readings said, in which St. Paul writes to the Romans (Romans 13:11-14). “For our salvation is nearer now than when we first believed; the night is advanced, the day is at hand. Let us then throw off the works of darkness and put on the armor of light; let us conduct ourselves properly as in the day, not in orgies and drunkenness, not in promiscuity and lust, not in rivalry and jealousy. But put on the Lord Jesus Christ, and make no provision for the desires of the flesh.”