From: Luke 1:57-66
The Birth and Circumcision of John the Baptist
 Now the time came for Elizabeth to be delivered, and she gave birth to a son.  And her neighbors and kinsfolk heard that the Lord had shown great mercy to her, and they rejoiced with her.  And on the eighth day they came to circumcise the child; and they would have named him Zechariah after his father,  but his mother said, "Not so; he shall be called John."  And they said to her, "None of your kindred is called by this name."  And they made signs to his father, inquiring what he would have him called.  And he asked for a writing tablet, and wrote, "His name is John." And they all marvelled.  And immediately his mouth was opened and his tongue loosed, and he spoke, blessing God.  And fear came on all their neighbors. And all these things were talked about through all the hill country of Judea;  and all who heard them laid them up in their hearts, saying "What then will this child be?" For the hand of the Lord was with him.
59. Circumcision was a rite established by God under the Old Covenant to mark out those who belonged to His chosen people: He commanded Abraham to institute circumcision as a sign of the Covenant He had made with him and all his descendants (cf. Genesis 17:10-14), prescribing that it should be done on the eighth day after birth. The rite was performed either at home or in the synagogue, and, in addition to the actual circumcision, the ceremony included prayers and the naming of the child.
With the institution of Christian Baptism the commandment to circumcise ceased to apply. At the Council of Jerusalem (cf. Acts 15:1ff), the Apostles definitely declared that those entering the Church had no need to be circumcised.
St. Paul's explicit teaching on the irrelevance of circumcision in the context of the New Alliance established by Christ is to be found in Galatians 5:2ff; 6:12ff; and Colossians 2:11ff.
60-63. By naming the child John, Zechariah complies with the instructions God sent him through the angel (Luke 1:13).
64. This miraculous event fulfills the prophecy the angel Gabriel made to Zechariah when he announced the conception and birth of the Baptist (Luke 1:19-20). St. Ambrose observes: `With good reason was his tongue loosed, because faith untied what had been tied by disbelief" ("Expositio Evangelii Sec. Lucam. in loc.").
Zechariah's is a case similar to that of St. Thomas, who was reluctant to believe in the resurrection of our Lord, and who believed only when Jesus gave him clear proof (cf. John 20:24-29). For these two men God worked a miracle and won their belief; but normally He requires us to have faith and to obey Him without His working any new miracles. This was why He upbraided Zechariah and punished him, and why He reproached Thomas: "Have you believed because you have seen Me? Blessed are those who have not seen and yet believe" (John 20:29).
Source: "The Navarre Bible: Text and Commentaries". Biblical text taken from the Revised Standard Version and New Vulgate. Commentaries made by members of the Faculty of Theology of the University of Navarre, Spain. Published by Four Courts Press, Kill Lane, Blackrock, Co. Dublin, Ireland. Reprinted with permission from Four Courts Press and Scepter Publishers, the U.S. publisher.