說無垢稱經疏 6.684

6.684

贊曰：二為授記。見其因修，復發願請，觀因見果，故為之記。正法如城，行者如人居城中住，月蓋能護正法，言能護法城。

The Commentary says: Second, conferring a prophecy. Seeing his causal practice and his further making vows and requests, the Buddha observed the cause and saw the fruit, and therefore prophesied for him. The True Dharma is like a citadel; practitioners are like people residing inside the citadel. Because Candrachattra was able to protect the True Dharma, it says he was "able to protect the citadel of the Dharma."