1)
Why did Moshe repeat what Gad and Reuven had said and not simply approve their request?
1.
Or ha'Chayim: Because Gad and Reuven spoke about going to fight before 'the B'nei Yisrael', Moshe pointed out that Jewish soldiers go to war (not before Yisrael, but) 'before Hashem!', emphasizing this point a number of times in his reply. 1
1
A lesson that they took to heart, as is evident in their reply in Pasuk 27.
