Luke 1:8–9 (ESV)

8 Now while he was serving as priest before God when his division was on duty,

Being introduced to this couple, our attention is directed next to Zechariah in the temple. Apparently, his division had been chosen to go on duty. Because of the many divisions and priests, a choice had to be made and this was done by lot. This time (and perhaps the only time) the lot fell on the division of Abijah to which Zechariah belonged, and he was charged with burning incense in the temple.