'Priestly' in the Bible

Now while he was doing priestly duty before God in the prescribed course of his class,

I call God to witness--to whom I render priestly and spiritual service by telling the Good News about His Son-- how unceasingly I make mention of you in His presence,

that I should be a minister of Christ Jesus among the Gentiles, doing priestly duties in connexion with God's Good News so that the sacrifice--namely the Gentiles--may be acceptable to Him, being (as it is)