English: “And you shall take” — this teaches that kiddushin (marriage acquisition) takes effect with her.
On the daf / in context: The verb “ve-lakachta” is the classic language of kiddushin. The Gemara therefore learns that the relationship is a genuine marriage: the offspring follow the father’s status, unlike the ordinary case of a non-Jewish woman who bears a child to a Jewish man.
Type of Learning
Derash on the verse (Bavli) — the verb of taking establishes full kiddushin.
What Is Learned
Once the captive woman is taken under the Torah’s procedure, full Jewish kiddushin takes effect and the children follow the father’s lineage.