Although Zacharias and Elizabeth were beyond childbearing years, they still prayed for a child, perhaps even a son, since they were childless, believing that all things are possible with the Lord.
Then the Lord answered their prayers and He sent Gabriel to Zacharias with the great news,

But the angel said to him,

“Do not be afraid, Zacharias, for your prayer is heard; and your wife Elizabeth will bear you a son, and you shall call his name John. And you will have joy and gladness, and many will rejoice at his birth” (Luke 1:13–14).

We know later that Zacharias doubted the message of Gabriel, nevertheless, the angel still revealed that Zacharias would have joy and gladness when their little boy entered the world.
However, this was not just any boy, but one chosen by the Lord to be His forerunner. So, while Zacharias and Elizabeth had to wait a long time for a child, when they finally received one, he became the greatest man ever, except for Jesus Christ.