大毘盧遮那成佛經疏 10.90

10.90

以初薩字為體是堅義。若有堅住即有生住異滅之相，入阿字本來無堅，則無成壞故也。餘字皆為釋此。私謂以此妙音悅可眾生，言辭柔軟悅可眾心令得歡喜者，說無堅令知無常，驗得如來堅固之法也。

Taking the initial syllable *sa* as the essence, it has the meaning of solidity. If there is solid abiding, then there are the characteristics of arising, abiding, changing, and ceasing; entering the syllable A, which is originally without solidity, there is consequently no formation or disintegration. The remaining syllables all explain this. In my personal opinion, pleasing sentient beings with this wondrous sound, using soft words to delight the minds of the multitude and make them joyful, one preaches non-solidity to make them aware of impermanence, verifying and attaining the solid Dharma of the Tathāgata.