(Devarim 21:10) "If you go out to war": Scripture speaks of an optional war (as opposed to a war of mitzvah).
"al your foes": against your foes.
"and the L-rd your G-d delivers him into your hand": If you do as stated herein, in the end, the L-rd your G-d will deliver him into your hand.
"and you capture its captivity": including Canaanites in their midst (even if they be of the seven nations).
(Ibid. 11) "and you see in the captivity": at the time of the captivity.
"a woman": even a married woman.
"of beautiful form": This tells me only of a woman of beautiful form. Whence do I derive that the same applies to an ugly woman? From "and you desire her": even if she is not beautiful. If so, why is it written of beautiful form"? Scripture speaks of the common instance.
"then you may take her for yourself as a wife": and not for his father and not for his son.