Why did Yaakov allow the members of his household to retain idols even for one moment (See Ibn Ezra)?
Ramban (to 35:4) and Seforno: In actual fact, the people of Shechem had nullified their gods, 1 in which case they were permitted. Nevertheless, Yaakov decided to get rid of them, before moving on to Beis El, in order to remove every trace of idolatry from their hearts.
Ohr ha'Chayim #1: Before they left, he warned them not to take idolatry of the nations (Shechem) into their possession, for then a Nochri cannot be Mevatel it. Only a Nochri who is expert in idolatry can be Mevatel it, therefore the women and children that they took from Shechem could not do so.
Ohr ha'Chayim #2: Perhaps his family did not know that after idolatry entered the Yisrael's Reshus, there is no Bitul.
Ohr ha'Chayim #3: Perhaps there was idolatry hidden in Kelim. Yaakov commanded them to check before taking things, to avert what is repulsive.
Ha'amek Davar: He did not say 'b'Yedchem,' for surely his family would not have idolatry that was not nullified. However, perhaps there is "b'Sochechem" - amidst the captives taken from Shechem for slaves.
Upon the instruction of the Bnei Yaakov - and an Avodah Zarah that a Nochri nullifies, even against his will, is permitted (Ramban).
What are the implications of "ve'Hitaharu"?
Semag (244): It implies that Avodah Zarah renders Tamei and that consequently, someone who separates from it requires Tevilah. 1
Ibn Ezra: They should bathe. One's body and clothing must be clean when he prays in a fixed place.
Malbim: They must eradicate also foreign mindsets and thoughts, and purify their deeds and change their bad Midos, which are called clothes.
Torah Temimah: Which explains why a convert requires Tevilah.
Why was it necessary to change their clothes?
Rashi: In case among the spoils that they had taken from Shechem, there were clothes that had been used for Avodah Zarah. 1
Ohr ha'Chayim: The Rambam (Hilchos Avodah Zarah 6:12) writes that anything that is Metamei one who moves it, he is Metamei the clothes he is wearing when he touches it.
Ibn Ezra: Refer to 35:2:1.1:2.
Ha'amek Davar: They needed to wash only "Simloseichem" - the outermost garment. This is why the Targum of "v'Chibsu Simlosam" (Shemos 19:10) is to launder, and not to immerse. If it were due to Tum'ah, it would apply to all garments!
Why does it say "Kol Asher Imo"?
Ha'amek Davar: This refers to people connected to Yaakov who understand and heed his words.
QUESTIONS ON RASHI
Rashi writes: "'And purify yourselves' - from idolatry." But perhaps it means to purify themselves from Tum'ah (in preparation for offering Korbanos)?
Gur Aryeh: We know this from context. The preceding phrase was "remove the foreign gods from amongst you." It is followed by, "and change your clothing;" would not immersion suffice to remove Tum'ah? Just as the clothing [from the spoils of Shechem] must be switched lest it contain idolatry, the "purification" of this phrase also must refer to purging of idolatry.
