Albert Barnes' Notes on the Whole Bible - Hebrews 9:7
But into the second - The second apartment or room, called the most holy place; Hebrews 9:3.Went the high priest alone once every year - On the great day of atonement; Exodus 30:10. On that day he probably entered the Holy of Holies three or four times, first to burn incense, Leviticus 16:12; then to sprinkle the blood of the bullock on the mercy-seat, Leviticus 16:14; then he was to kill the goat of the sin-offering, and bring that blood within the Veil and sprinkle it also on the mercy-seat,... read more
The Pulpit Commentary - Hebrews 9:7-8
But into the second the high priest alone, once in the year, not without blood, which he offereth for himself and for the errors (literally, ignorances ; cf. Hebrews 9:2 ) of the people. For the ceremonies on the Day of Atonement, see Leviticus 16:1-34 . They may be summarized, in their main characteristics, thus: read more