The place of this altar in the tabernacle has been a problem for some readers of the Book of Hebrews. Hebrews 9:4 can be understood as describing its location as being inside the holy of holies with the ark. The writer of Hebrews probably meant that the veil, not the holy of holies, had the altar of incense and the ark of the covenant connected with it ( Hebrews 9:3-4). These pieces of furniture were on either side of the veil. Describing it this way clarified that the writer meant the veil between the holy place and the holy of holies. Old Testament passages say that the incense altar was inside the holy place with the golden lampstand and the table of showbread (cf. Exodus 30:6; Exodus 40:3-5; Exodus 40:21-27). Most commentators on Exodus locate it in the holy place. [1] Furthermore, Leviticus 16:2 and Hebrews 9:7 say that the high priest went into the holy of holies only once a year on the Day of Atonement. Another view is that the altar of incense was in the holy of holies. [2][source]
The priests would offer incense on this altar each morning and each evening, and the incense would burn all the time. The priests presented the daily burnt offering and the daily incense offering together each day. Both were demonstrations of constant uninterrupted devotion to God. Students of Exodus have almost universally recognized the incense offered as a symbol of prayer that ascends to God (cf. Revelation 5:8). It was a sweet aroma in His nostrils and was essential to the maintenance of the divine-human relationship. [source][source][source]
"Morning and evening prayers have been the habit of all ages. With the one we go forth to our labour till the evening, asking that our Father will give us His God-speed and guidance and protection. With the other we entreat forgiveness and mercy." [3][source]
"He who offers no sacrifice in his prayer, who does not sacrifice his self-will, does not really pray." [4][source]
The horns of this altar ( Exodus 30:10), as well as the horns on the altar of burnt offerings (the brazen altar), probably symbolized strength. [5][source]
Once a year Aaron applied the atonement blood on this altar to cleanse it afresh for another year ( Exodus 30:10). The description "most holy to the LORD" means the altar could not be used for any other purpose than what is stated here. [source][source][source]
The directions concerning the sanctuary conclude with this section. [source][source][source]