Zachariah in the Temple
The priest who attended to the incense service entered the Holy Place, and received from his assistant the incense. It was placed into his cupped palms. [Note:The Hebrew idiom for appointing to an office is "to fill the hand, " alluding to the offerings placed in the hand--authorizing him to act as priest. See Exodus 29 (Hertz Chumash, pg 435)] The coals from the outer altar were placed on the top of the inner altar and then the assistant retired from the room.
The priest was left in the sanctuary alone while all of the other priests were waiting outside. The Jewish writings say that after the overseer gave the signal to burn the incense, the priest began to let the grains fall slowly from his palms across the top of the altar. When the entire chamber filled with the cloud of incense, the priest prostrated himself in adoration and went out of the sanctuary (Mishnah Tamid 6:3).
The scene just described happened every morning and evening. Whenever the people saw the smoke of the incense offering, which they believed to be a symbol of true consecration to God, they fell down before the Lord and spread their hands out in silent prayer. They arose when the priest who had make the offering came out to recite the blessing.
Going into the Holy Place always carried with it a sense of danger (see 2 Chronicles 26:16-23). And there was a rabbinic tradition that if a priest were going to die, an angel would be standing on the right side of the altar of incense (Jerusalem Talmud, Yoma 42c). The priests were admonished to quickly come out after completing their duties lest they "terrify Israel" and cause the people to fear that their prayers were not accepted. To show his relief at making it out in good condition, the priest sometimes prepared a feast for his friends the hour he came forth (Yoma 7:4).
No wonder the presence of the angel Gabriel caused Zachariah to be fearful and troubled.