+Lk 1: 57-66. 80
When the time arrived for Elizabeth to have her child she gave birth to a son.
Her neighbors and relatives heard that the Lord had shown his great mercy toward her, and they rejoiced with her.
When they came on the eighth day to circumcise the child, they were going to call him Zechariah after his father,
but his mother said in reply, “No. He will be called John.”
But they answered her, “There is no one among your relatives who has this name.”
So they made signs, asking his father what he wished him to be called.
He asked for a tablet and wrote, “John is his name,” and all were amazed.
Immediately his mouth was opened, his tongue freed, and he spoke blessing God.
Then fear came upon all their neighbors, and all these matters were discussed throughout the hill
All who heard these things took them to heart, saying, “What, then, will this child be?” For surely the hand of the Lord was with him.
The child grew and became strong in spirit, and he was in the desert until the day of his manifestation to Israel.
The New American Bible
The Catechism of the Catholic Church
522 The coming of God’s Son to earth is an event of such immensity that God willed to prepare for it over centuries. He makes everything converge on Christ: all the rituals and sacrifices, figures and symbols of the “First Covenant”. He announces him through the mouths of the prophets who succeeded one another in Israel. Moreover, he awakens in the hearts of the pagans a dim expectation of this coming.
523 St. John the Baptist is the Lord’s immediate precursor or forerunner, sent to prepare his way. “Prophet of the Most High”, John surpasses all the prophets, of whom he is the last. He inaugurates the Gospel, already from his mother’s womb welcomes the coming of Christ, and rejoices in being “the friend of the bridegroom”, whom he points out as “the Lamb of God, who takes away the sin of the world”. Going before Jesus “in the spirit and power of Elijah”, John bears witness to Christ in his preaching, by his Baptism of conversion, and through his martyrdom.
524 When the Church celebrates the liturgy of Advent each year, she makes present this ancient expectancy of the Messiah, for by sharing in the long preparation for the Savior’s first coming, the faithful renew their ardent desire for his second coming. By celebrating the precursor’s birth and martyrdom, the Church unites herself to his desire: “He must increase, but I must decrease.”
The Nativity of John the Baptist
The Nativity of John the Baptist (or Birth of John the Baptist, or Nativity of the Forerunner) is a Christian feast day celebrating the birth of John the Baptist, a prophet who foretold the coming of the Messiah in the person of Jesus, whom he later baptised.