大毘盧遮那成佛經疏 17.36

17.36

次va字水說名（謂想嚩即同水也）。次想ra，即同火也。次想吽，即一切忿怒持明也。又想佉字，即同空也（當有訶字即是風。今欠之，更問，即是也）。所以作此觀者，欲布一切字於是身分，即是一切如來法界之法萬德皆備。猶如坐道場時，非金剛坐則不能勝。今亦如是，欲備一切如來功德，先須用此地水火風四輪及空，然後作具法也。以能如是第一真實，若解者得阿闍梨名。壇中名字雖殊，皆是諸佛功德，為度彼故說也。是故諸佛說一切應知，常作勤修者能得不死句。猶阿闍梨以阿字加其身，故即是漫荼羅一切大會天等也。了達其義，即是真實阿闍梨也。次勸常當如是修行即得不死句，是常住義，常住即佛也。

Next, the syllable va is spoken of as water (meaning visualizing va as identical to water). Next, visualize ra, which is identical to fire. Next, visualize hūṃ, which is all wrathful vidyādharas. Again, visualize the syllable kha, which is identical to space (there should be the syllable ha, which is wind; it is missing here, and upon further inquiry, this is it). The reason for performing this visualization is to place all the syllables on these parts of the body, so that the dharmas of the dharmadhātu of all Tathāgatas, with their myriad virtues, are fully complete. Just as when sitting in the bodhimaṇḍa, without the vajra seat one cannot overcome [the māras], here too, wishing to be equipped with all virtues of the Tathāgatas, one must first use these four wheels of earth, water, fire, and wind, as well as space, and only then perform the full rite. Because of this supreme reality, one who understands it attains the name of ācārya. Although the names in the maṇḍala differ, they are all the virtues of the Buddhas, expounded to deliver them. Therefore, the Buddhas speak of all that should be known; those who always diligently practice will attain the state of the deathless (amṛtapada). Because the ācārya empowers his body with the syllable A, he is all the deities in the great assembly of the maṇḍala. Comprehending its meaning, he is a true ācārya. Next, it exhorts that by always practicing in this way, one attains the state of the deathless; this has the meaning of eternal abiding, and eternal abiding is the Buddha.