Jamieson, Fausset and Brown on Leviticus 9:23

23. Moses and Aaron went into the tabernacle--Moses, according to the divine instructions he had received, accompanied Aaron and his sons to initiate them into their sacred duties. Their previous occupations had detained them at the altar, and they now entered in company into the sacred edifice to bear the blood of the offerings within the sanctuary.

the glory of the Lord appeared unto all the people--perhaps in a resplendent effulgence above the tabernacle as a fresh token of the divine acceptance of that newly established seat of His worship.