Before Aaron's household held the priesthood, someone else did. Targum Pseudo-Jonathan on Exodus (Exodus 24:5) preserves this little-known tradition: Mosheh sent the firstborn of the sons of Israel,-for until that hour had the firstborn had the office of performing worship, the tabernacle of ordinance not as yet being made, nor the priesthood given unto Aharon; and they offered burnt offerings and consecrated oblations of oxen before the Lord.
The Original Priesthood of Israel
The Targum explains what the plain text glosses over. Until that hour, the firstborn sons of each household were the priests of Israel. They performed the family sacrifices. They led the household worship. This was the ancient order, stretching back to the patriarchs — Abraham built altars, Isaac and Jacob built altars, and their firstborn descendants carried the role forward.
At the foot of Sinai, this was still the arrangement. The Tabernacle had not been built. Aaron had not been consecrated. So Moses sent the firstborn to bring the burnt offerings that would seal the covenant.
The Transition to the Levitical Priesthood
This arrangement would soon change. After the golden calf, the firstborn were disqualified — they had failed to restrain the people from idolatry. The tribe of Levi, who rallied to Moses in the aftermath, received the priesthood in their place (Numbers 3:12). What we now call the Jewish priesthood — the kohanim descended from Aaron — was not the original order. It was a reassignment.
The Takeaway
Spiritual leadership in Israel is not fixed by inheritance alone. The firstborn had the role by birth. They lost it by choice. The Levites earned it by courage. The Torah teaches that covenantal privilege is responsive to covenantal faithfulness — always.