Bible Verses About Priests: All except seed of Aaron excluded from being

To Aaron and to his sons, to whom they are delivered by the children of Israel. But thou shalt appoint Aaron and his sons over the service of priesthood. The stranger that approacheth to minister, shall be put to death.

That the children of Israel might have for the time to come wherewith they should be admonished, that no stranger or any one that is not of the seed of Aaron should come near to offer incense to the Lord, lest he should suffer as Core suffered, and all his congregation, according as the Lord spoke to Moses.

But thou and thy sons look ye to the priesthood: and all things that pertain to the service of the altar, and that are within the veil, shall be executed by the priests. If any stranger shall approach, he shall be slain.