What does Luke 1:5 mean?
The explanation of John the Baptist's birth begins with an historical note. As a Gentile, writing mostly to other Gentiles, Luke often explains points which would have been obvious to a Jewish reader. Rather than simply using Herod as a time reference (Matthew 2:1), Luke specifies that Herod was king of Judea. This is the same king who will drive Jesus and His family into hiding in Egypt (Matthew 2:13–15). They will return after the ruler's death (Matthew 2:19–20).Under Old Testament law, only Levites, specifically descendants of Aaron, could serve as priests (Exodus 40:15; Numbers 25:13). Aaron's line was divided into 24 groups, who rotated in service in the temple each year (1 Chronicles 24). One of the priests of the "division" of Abijah is an older man named Zechariah, married to Elizabeth. They are childless. In that era, this was a mark of embarrassment and misfortune (Luke 1:24–25). Because of their age, they have no reasonable expectation that they will ever have children (Luke 1:7).
Fortunately for this faithful couple (Luke 1:6), God has a plan for them which includes the blessing of a child.