Well.. if you think about it he also indirectly gave naruto the kyuubi also. :D
If Zetsu is the one giving him the new arms it would make sense.. he is able to make real body clones and shit after all.I don't remember the chapter, it was around the time Naruto etc caught up with Sasuke just after he killed Danzou. Madara warped somewhere and was with zetsu and kinda...grew a new arm lol
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