He shall be called John. (Luke 1: 63)
Now the time came for Elizabeth to give birth, and she bore a son. And her neighbours and relatives 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 called him Zechariah after his father, but his mother answered, “No; he shall be called John.” And they said to her, “None of your relatives is called by this name.” And they made signs to his father, inquiring what he wanted him to be called. And he asked for a writing tablet and wrote, “His name is John.” And they all wondered. And immediately his mouth was opened and his tongue loosed, and he spoke, blessing God. And fear came on all their neighbours. 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. And the child grew and became strong in spirit, and he was in the wilderness until the day of his public appearance to Israel. (Luke 1: 57-66: 80)
Zachariah renounces giving a name he chose for his son. His son will now be called John, as duly requested by God. This renunciation is a big sacrifice for Zachariah since John is his only son due to his very advanced age, among other reasons. But if we think about it, Zachariah is only applying the "therefore" that we should all use. The reasoning is simple: if God asks me to name my son John, therefore I must obey and call him John. Let us remember that every logical "therefore" we offer to follow God’s Will, despite some sacrifice we make, will be amply rewarded, sometimes already during our lives on earth, just as it was for Zechariah who saw his son grow in holiness.