שַׁ֭אֲלוּ שְׁל֣וֹם יְרוּשָׁלִָ֑ם יִ֝שְׁלָ֗יוּ אֹהֲבָֽיִךְ׃
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Ibn Ezra
His tabernacle was in Shalem – This is referring to Jerusalem. Perhaps she is called Shalem because she is perfectly positioned opposite the gate of heaven, or that she is fit to be in peace. Or perhaps they called her thus in a prayerful fashion, like “ask for the peace of Jerusalem…” (Tehillim 122:6)