大毘盧遮那成佛經疏 7.7

7.7

經云「祕密主！云何真言法教」者，即謂阿字門等是真言教相。雖相不異體、體不異相，相非造作，修成不可示人，而能不離解脫現作聲字，一一聲字即是入法界門，故得名為真言法教也。至論真言法教，應遍一切隨方諸趣名言。但以如來出世之迹始于天竺，傳法者且約梵文作一途明義耳。

The sūtra says: 'Secret Lord! What is the mantra teaching?' This means that the syllable A gateway and so forth are the phenomenal characteristics of the mantra teaching. Although the characteristics are not different from the essence, and the essence is not different from the characteristics, the characteristics are not fabricated, and having been accomplished through cultivation, they cannot be shown to others; yet, without departing from liberation, they manifest as sounds and syllables, each sound and syllable being a gateway to enter the dharmadhātu; hence it is called the mantra teaching. Ultimately speaking, the mantra teaching should pervade all names and words across all regions and destinies. It is only because the traces of the Tathāgata's appearance in the world began in India that those who transmitted the Dharma have provisionally clarified its meaning in terms of Sanskrit.