Theophylact of Ohrid

When did his turn come to burn incense? Without doubt, on the day of atonement, when the high priest alone entered the Holy of Holies, so that we might learn that just as this high priest, having entered the Holy of Holies, received fruit, so too the Lord Jesus, the one and truly great High Priest, having entered the Holy of Holies, that is, with His flesh into heaven, received the fruit of His manifestation in the flesh — our adoption by God and salvation.

Commentary on Luke ↗

Bede

By lot he was chosen to burn incense when he entered the temple of the Lord; and the whole multitude of people was praying outside at the hour of incense. He was not chosen by a new lot, for it was the incense to be burned, but he had been chosen by an ancient lot when first in the order of his priesthood he succeeded in the division of Abijah. But it was commanded that incense be carried into the Holy of Holies by the high priest, while all the people were waiting outside the temple, on the tenth day of the seventh month. …

On the Gospel of Luke ↗

Bonaventure

Thirdly, he indicates it was done in the due manner on account of the attendance of the multitude, when he says: And the whole multitude of the people was outside, praying at the hour of incense. All were obliged to attend and pray together, according to what is said in Acts one: "All were persevering unanimously in prayer." And they stood outside out of reverence, as that publican in Luke eighteen: "The publican, standing afar off, did not dare," etc. …

Commentary on Luke, Chapter 1 ↗