Charles Ellicott Commentary Leviticus 16:12

"and he shall take a censer full of coals of fire from off the altar before Jehovah, and his hands full of sweet incense beaten small, and bring it within the veil:" — Leviticus 16:12 (ASV)

A censer full of burning coals. — After the bullock was slain, and before its blood was sprinkled, the high priest took the censer, which on this occasion was a golden one, and filled it with brightly glowing coals. These he took from that part of the ever-burning fire on the altar of burnt offering or brazen altar which was on the west side, toward the Holy of Holies, where the Lord dwelt. This is the sense which the canonical law attached to the phrase “before the Lord” here.

And his hands full of sweet incense. — Having provided himself with two handfuls of the finest incense, and holding the censer with the fire in his right hand, and the cup with the incense in his left, he now entered for the first time through the second veil into the Holy of Holies, advanced to the ark of the covenant, and deposited the censer between its two staves. During the Second Temple period, he stepped forward to the stone that was the substitute for the Ark and placed the censer upon it.