Luke 1:10

And the whole multitude of the people were praying without at the time of incense.

It so happened, or rather it came about by God's dispensation and government, that Zacharias was serving in his priestly office. In the course of time, as it happened twice a year in the Jewish calendar, his order or division was on duty in the Temple of the Lord. So he left his home and went to Jerusalem for the week's duties with the other priests of his course. It was the custom of the Jews to designate the various labors which the priests had to perform in the Temple by casting lots, some of them being selected to take care of the altar of burnt offerings, others to the appointments of the Holy Place, others to the vessels in the priests' court. In this way it fell to the lot of Zacharias on a certain day to perform the very special service of burning incense on the golden altar in the Holy Place. This was a memorable day in the life of any priest, since the chance might never come to him but once. This work was performed in the Temple proper, as Luke remarks for the sake of such as were not familiar with the Jewish form of worship and the various offerings in the services. The officiating priest, during this part of the ceremony, was in the Holy Place all alone, all the attendants and assistants having withdrawn. The congregation, during this ceremony, was assembled out in the courts, for this was the hour of prayer, about nine o'clock in the morning, and the offering of incense was a type and symbol of the prayers arising to the throne of God, Psalms 141:2.