Why did they take the women and children captive?
Moshav Zekenim (to 34:26): Neighboring residents had relatives in Shechem. They needed to make peace with Bnei Yaakov in the eyes of all the nations [for the sake of their relatives]. Because they made peace with the surrounding residents, Yosef was later able to go alone to Shechem (37:13-17).
Oznayim la'Torah: It was spoils of war - just as Shechem and Chamor planned to do to them.
What is the difference between "Shavu," "va'Yavozu" and "Lakachu" (34:28)?
Malbim: Shevi refers to human captives. Va'Yavozu is all their wealth, and what is in the house.
Ha'amek Davar (to 34:28,29): Lakachu means that they acquired ownership. Animals that people feed, if they have no owner, they will die! Kelim in the house, they did not need to take all of them. Shavu is what they took for themselves. Va'Yavozu is what they left Hefker for others. 1
Ha'amek Davar: When the Zayin is doubled (Bazezu), it means that they took from the owner with adamancy to get everything.
QUESTIONS ON RASHI
Rashi writes: "'Shavu' - i.e. they took captive (from the word 'Shivyah')." How can we prove this?
Gur Aryeh: The word "sha-VU'" is accented on the final syllable (Mi'lera). [Were it to mean "they returned" (from the word 'la'Shuv'), the accent would be on the first syllable (Mi'le'eil) -- SHA-vu.] 1
Gur Aryeh: In other words, the Shoresh of our word is Shin-Beis-Hey (and not Shin-Vav-Beis).
