God himself dwelt in the tabernacle/temple in the Old Testament. The only people physically permitted inside the temple were priests (Numbers 16:40; Numbers 18:7). In the new dispensation, Christians (individually and collectively) are a temple of the Lord in whom the Lord dwells by his Spirit (1 Corinthians 3:16; 1 Corinthians 6:19). That means that God has made every believer a priest, suitable to be in his presence. Given that God is holy (Lev. 10ff.), those who are in his presence need also to be holy; hence the need for specific laws in the Old Testament to guard the sanctity of the priests (Lev. 21ff.). Similarly, as all God’s people are now his temples, every Christian is a holy priesthood and hence is to be holy and priestly, all the time since we are always temples of the Spirit.
5 you yourselves like living stones are being built up as a spiritual house, to be a holy priesthood, to offer spiritual sacrifices acceptable to God through Jesus Christ.