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hIn verses 3 and 4, it is called Aron Hashem. Why did they now call it "Aron Elokei Yisrael" and "Aron Elokim" (verse 10)?
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Kli Yakar (Lani'ado): It brings judgments (like Elokim), and avenges [what we did to] Yisrael. Or, it desires to return to its land, to be Elokei Yisrael (e.g. when the Kohanim said to return it - 6:3).