"Put away the idols of the peoples which are among you, which you took from the temple of Shekem, and purify you from the uncleannesses of the slain whom you have, and change your raiment." Targum Pseudo-Jonathan (Genesis 35:2) reveals a detail the plain text leaves vague: the idols in Jacob's household had been taken as plunder from the sack of Shechem.
Think about what that means. After Simeon and Levi killed the men of the city, some of Jacob's household picked through the temple and carried away the sacred objects of a foreign cult. The idols had come home with them as trophies. And they had stayed.
Three commands to purify
Jacob gave three commands at once. Remove the idols. Wash from the impurity of contact with the dead. Change your clothes. It is a complete decontamination protocol — physical, spiritual, and ritual.
The rabbis noticed the order. You cannot go up to Bethel with idols in your baggage. You cannot meet the Holy One while still wearing the dust of the slain. And you cannot wear the same clothes in which you did questionable things and expect the sacred to settle on you. Before the ascent, the purge.
The takeaway: return to God requires leaving something behind — and the things you have to leave are usually the things you should have left long ago.