The First Reading is from the Book of the Prophet Isaiah 11:1-10. To help us prepare for the coming of Christ at Christmas, the Church recalls the prophecies of the great Isaiah on each of the four Sundays of Advent. To encourage the Chosen People who, because of the bad example of their worldly leaders, were wavering in their loyalty to Yahweh their true God, the prophet reminds them of him who is to come.
The Second Reading is from the Letter of St. Paul to the Romans 15:4-9. St. Paul is telling newly converted Christians, converted Christians of Rome, many of whom were Jews, that the sacred Scriptures of the Old Testament are still a source of instruction, encouragement, and hope. The call of Abraham and the promises made to him, and to his descendants, were fulfilled in the coming of Christ.
The Gospel is from the Gospel of Matthew 3:1-12, an angel announced to Zechariah, a priest of the temple, that he would have a son (even though his wife Elizabeth was barren and advanced in years). This son was destined to be the Precursor who would announce the proximate arrival of the long-expected Messiah.