Unlike the Old Testament priesthood, in which only those who were born into a certain tribe could be priests, all who are re-born into God’s family, that is believers, are priests who have the privilege and responsibility of offering spiritual sacrifices unto God.
Romans 12:1-2 1 I beseech you therefore, brethren, by the mercies of God, that ye present your bodies a living sacrifice, holy, acceptable unto God, which is your reasonable service. 2 And be not conformed to this world: but be ye transformed by the renewing of your mind, that ye may prove what is that good, and acceptable, and perfect, will of God.