大毘盧遮那成佛經疏 13.13

13.13

"At that time, the World-Honoured One dwelt in the samādhi of the unassailable bodily power": in order to fulfill this wish, the Buddha again entered samādhi. This is the sovereign power of the Tathāgata's immeasurable body, and therefore none can harm it. Dwelling in this samādhi, he uttered the three-vidyā mantra; its vidyā is named unhindered, unassailable, and unequalled power. By virtue of this samaya, all learners are able to hear and enter the true Dharma. If one does not perform it, one is not qualified to enter the altar, nor qualified to hear the secret teaching. If one cultivates this vidyā, one can attain purity of body and purity of speech, have one's wishes fulfilled, and unite with the three bodies; hence it is called the three vidyās. The three powers refer to the power of the three times or the power of the three equalities. The unequalled power is these very three powers. Its vidyā will be explained next.