What does Luke 1:64 mean?

When the angel Gabriel told Zechariah he would become a father (Luke 1:13), the elderly priest reacted with doubt (Luke 1:18). As a result, he was rendered "silent and unable to speak until the day that these things take place" (Luke 1:19–20). That day has finally come. Zechariah's wife, Elizabeth, has given birth (Luke 1:57), and she has insisted on the name "John" (Luke 1:60). Zechariah confirmed this in writing (Luke 1:63), much to the amazement of others.

That moment completes the angel's prophecy about the birth of this child. Zechariah is enabled to speak—as one would expect, his first words celebrate God's blessing. There would have been great publicity around this pregnancy, given its unusual circumstances (Luke 1:37). Most likely, there are more people than usual present for the baby's circumcision and naming ceremony (Luke 1:59; Leviticus 12:3). This will enhance the reputation around John the Baptist (Luke 3:2–3) even while he is still an infant (Luke 1:65–66).