What are "Otzeros Choshech"?
Radak: A person stores silver, gold and gems under the land in a dark, hidden place. Bavel had many storehouses. It is called Madhevah - it has much Zahav.
Malbim: They are treasures in hidden places.
How will he know who is Hashem?
Radak: Your victory to subdue kings of lands under you will not be with armies or strength, rather, with My sprit and desire. Koresh recognized this - "Kol Mamalachos ha'Aretz Nasan Li Hashem Elokei ha'Shamayim" (Ezra 1:2). The previous kings were haughty and did not recognize Kel until He sent His hand against them. E.g. Melech Ashur said "b'Cho'ach Yadi Asisi uv'Chachmasi Ki Nevonosi" (above, 10:13). Nebuchadnetzar said "E'eleh Al Bamasi Av Adameh l'Elyon" (14:14). Therefore, Koresh contemplated and saw that the early [kings] were haughty and fell in Kel's hand. He recognized that it is Kel's strength; all is in His hand. He raises and lowers.
Malbim: Hashem will hand over to him the storehouses and hidden treasures.
Why does it say "ha'Korei v'Shimcha"?
Rashi: You were not born yet, and I call you 'Koresh'.
Malbim: I aggrandize you unlike nature.
