Either he killed the goat before he entered into the holy of holies, though it be mentioned after, such transplacings of passages being not unusual; or rather he went out of the holy of holies and killed it, and then returned thither again with its blood, and this agrees best with the text, nor are transpositions to be allowed without necessity. And whereas the high priest is said to be allowed to enter into that place but once in a year, that is to be understood but one day in a year, though there seems to have been occasion of going in and coming out more than once upon that day.
Related Commentaries of Leviticus 16:15
Leviticus 16:15
15 Then shall he kill the goat of the sin offering, that is for the people, and bring his blood within the vail, and do with that blood as he did with the blood of the bullock, and sprinkle it upon the mercy seat, and before the mercy seat: