Similarly, (Psalms 29:8) "The voice of the L-rd frights the desert; the L-rd frights the desert of Kadesh." Now is it not already written "the voice of the L-rd frights the desert"? (Why, then, is it written, etc.)
(Devarim 11:12) "a land which the L-rd your G-d inquires after": It is subject to inquiry for the separation of challah, terumoth, and tithes. I might think that the other lands are also subject to inquiry; it is, therefore, written "inquires after it"; it is subject to inquiry and not the other lands.