John the Baptist appeared, preaching in the desert of Judea and saying, "Repent, for the kingdom of heaven is at hand!" It was of him that the prophet Isaiah had spoken when he said: "A voice of one crying out in the desert, Prepare the way of the Lord, make straight his paths." At that time Jerusalem, all Judea, and the whole region around the Jordan were going out to him and were being baptized by him in the Jordan River as they acknowledged their sins. (Mt 3:1-12)
https://bible.usccb.org/bible/readings/120422.cfm
In addition to the Prophet Isaiah, John the Baptist is one of the most important figures of this first part of Advent. Our mission, like John the Baptist, is to prepare the way of the Lord in our world, in our lives. Perhaps it’s as simple as Saint Paul says: “Welcome one another as Christ welcomed you.”