大毘盧遮那成佛經疏 14.46

14.46

凡布漫荼羅亦為三重，第一重迦字乃至訶，周匝內重，名為金剛輪也。此金剛輪持一切法，猶如世界金剛之輪持於世界也，即是行者最初菩提心輪。謂欲堅固菩提心故，先作內重也。次第二輪謂阿暗，此是長阿及暗二輪，同是中分。若用迦為輪，即不須用欠字輪也（私謂迦是行者因，欠是證是果也）。次第三輪用惡字輪，亦順中如上布之，令環合也。其伊等十二字在外散布，猶如光焰也。此即是三轉法輪之義也。如是布已，持誦者即是持明之身，猶如大日如來神力加持等無有異。此輪亦名因緣輪也。師及弟子并漫荼羅，皆作如是祕密之輪。又此諸字即是真言之輪，故凡有四種輪也。又字輪者，梵音云噁剎囉輪，噁剎羅是不動義，不動者所謂是阿字菩提心也。如毘盧遮那，住於菩提心體性，種種示現普門利益，種種變現無量無邊。雖如是垂迹無窮盡，能實常住不動，亦無起滅之相。猶如車輪雖復運轉無窮，而當中未曾動搖，由不動故，能制群動而無窮極也。此阿字亦復如是，以無生故即無動無退，而生一切字輪轉無窮，是故名不動輪也。若行者能了達如是不動之輪而布諸明，即以其體自然，身有所表無非密印，口有所說悉是真言。凡有見聞觸知之者，皆必定於無上菩提所成福利，真不虛也。如能如是，即同毘盧遮那而作佛事，常照世間也。

In general, arranging the maṇḍala also involves three tiers. In the first tier, the syllables from ka to ha encircle the inner tier, which is called the vajra wheel. This vajra wheel supports all dharmas, just as the world's vajra wheel supports the world; it is precisely the practitioner's initial bodhicitta wheel. That is to say, because one wishes to solidify the bodhicitta, one first creates the inner tier. Next, the second wheel refers to ā and aṃ; these two wheels of long ā and aṃ belong together to the middle division. If one uses ka for the wheel, then there is no need to use the wheel of the syllable kha (my personal note: ka is the practitioner's cause; kha is the realization, the fruit). Next, the third wheel uses the wheel of the syllable aḥ; this is also arranged along the center as described above, making the circle close. Its twelve syllables such as i are dispersed outside like blazing rays of light. This is the meaning of the three turnings of the wheel of the Dharma. Having arranged it thus, the practitioner reciting [the mantras] is the embodiment of the vidyādhara, equal and without distinction, just like the supernatural adhiṣṭhāna of Mahāvairocana Tathāgata. This wheel is also named the wheel of causes and conditions. The master, the disciple, and the maṇḍala all make such secret wheels. Moreover, these syllables are the wheel of mantras, and therefore there are four kinds of wheels altogether. Furthermore, regarding the 'wheel of syllables', the Sanskrit pronunciation is akṣara-cakra. Akṣara has the meaning of unmoving; what is unmoving is the syllable A, bodhicitta. Just as Vairocana abides in the nature of bodhicitta, manifesting diverse universal-gate benefits and transforming into countless, boundless [forms]—although he thus displays traces without end, his real nature constantly abides unmoving, having no marks of arising or ceasing. Just as a carriage wheel, though turning without end, never shakes at its center, and because it is unmoving it can govern all movements without limit, this syllable A is also like this: because it is unborn, it is unmoving and non-regressing, yet it generates all syllables, revolving without end; therefore, it is called the unmoving wheel. If a practitioner can thoroughly understand such an unmoving wheel and arrange the vidyās, then by their nature, spontaneously, whatever the body expresses is nothing other than a secret mudrā, and whatever the mouth speaks is entirely mantra. All those who see, hear, touch, or perceive it will certainly attain the supreme bodhicitta; the merits and benefits accomplished are truly not in vain. If one can be like this, one acts to perform the Buddha's deeds together with Vairocana, constantly illuminating the world.