Rashi Studies (Advanced)

The verse that starts the discussion of female captives of war refers to a non-obligatory war. How does Rashi know this?

Why does Rashi call the mitzvah of sending away the mother bird before taking the chicks "a very easy mitzvah"?

Does the prohibition of shatnez more closely resemble the prohibition of plowing with an ax and a donkey together, or the prohibition of the mixing of seeds? A comparision of Rashi, Rambam, and Rabbeinu Tam.