1Peter 2:5 and 9 tell us that all Christians are priests. Peter quotes Isaiah 8 and Isaiah 28 to establish his case.
Both passages are remnant passages. The nation of Israel as a whole is condemned by God but within the nation there is a faithful remnant who put their hope in the Lord and gather around his prophet.
In both Isaiah 8 and Isaiah 28, the Lord promises to be with this remnant, to be their sanctuary. So it is that the true sanctuary is not the temple in Jerusalem, but the Lord himself. The true people are not those who have the national religion but those who put their hope in their Lord's promise.
Isaiah's Doctrine of the Priesthood of All Believers
