English: “Of beautiful form” — the Torah spoke only in response to the evil inclination. Better that Israel eat the meat of animals that are about to die but have been properly slaughtered than that they eat the meat of animals that have already died of themselves.
On the daf / in context: The classic baraisa on Kiddushin 21b explains the entire captive-woman permission as a concession to the yetzer hara. If the Torah had forbidden her outright, the soldier would take her in sin; the Torah therefore channels the desire into a regulated process that ultimately protects both parties.
Type of Learning
Derash on the verse (Bavli sugya) — not a formal named middah of the 13; the Gemara presents the law as a concession to the yetzer hara.
What Is Learned
The captive-woman permission is a concession to human desire; better a regulated path than outright prohibition that would be violated.