Ezekiel 44:9-11

9This is what the Sovereign LORD says: No foreigner uncircumcised in heart and flesh is to enter my sanctuary, not even the foreigners who live among the Israelites. 10“ ‘The Levites who went far from me when Israel went astray and who wandered from me after their idols must bear the consequences of their sin. 11They may serve in my sanctuary, having charge of the gates of the temple and serving in it; they may slaughter the burnt offerings and sacrifices for the people and stand before the people and serve them.