Adam Clarke on Luke 1:10

The whole multitude - were praying - The incense was itself an emblem of the prayers and praises of the people of God: see Psa 141:2; Rev 8:1. While, therefore, the rite is performing by the priest, the people are employed in the thing signified. Happy the people who attend to the spirit as well as the letter of every divine institution! Incense was burnt twice a day in the temple, in the morning and in the evening, Exo 30:7, Exo 30:8; but the evangelist does not specify the time of the day in which this transaction took place. It was probably in the morning.