The Targum Pseudo-Jonathan on Exodus 29:30 legislates how the high priesthood is passed on. For seven full days, the son who rises after his father wears the vestments and enters the tabernacle of ordinance. Then — and only then — does the succession take effect. The Targum adds a sharp clarification the plain verse leaves silent: the successor must come from Aaron's sons, but not from the Levites.
The distinction matters. Levites served in the sanctuary. They carried, sang, guarded, and assisted. But the high priesthood belonged to one specific family inside one specific tribe. The Targum closes a door that could otherwise have drifted open over centuries — no transfer sideways into the wider Levitical family, no elevation by merit alone, no workaround.
Seven days of transition also matters. The Sages read the number as a full cycle of creation. A new priest had to live through every day of the week in the vestments before the title was truly his. Whatever holiness the office conferred, it conferred gradually. No one became a high priest by putting on the robe once. He became a high priest by waking up in it seven mornings in a row.
The takeaway is about authority. Genuine office is inherited, earned through time, and fenced in by specifics. The Targum's small clause — but not from the Levites — is a reminder that holiness has borders, and the borders keep the work honest.