大毘盧遮那成佛經疏 14.38

14.38

祕密主！如是等佛信解生菩薩摽者，如來已證平等法界，以本所願大悲力故，以神力加持而現此方便身密之門，為令一切眾生皆得信解，同入一切智地。是故如是等印，當知從佛信解生也。當知如是印等，是諸菩薩之摽幟也。謂以此方便示如來內證之德，故云摽也。如印眾多，乃至身分舉動止住皆是印者，若阿闍梨明解瑜伽，深達祕密之趣，能淨菩提之心，以心淨通達祕密法故，凡有所作皆為利益調伏眾生，隨所施為無不隨順佛之威儀，是故一切身所有舉動施為無不是印也。何但身業而已？乃至一切所有語言亦復皆是真言也。

Lord of Mysteries! As for "such emblems of the bodhisattvas born of faith and understanding in the Buddha": The Tathāgata has already realized the equal dharmadhātu, and by the power of his original vow and great compassion, he manifests this gateway of the body mystery of upāya through the adhiṣṭhāna of supernatural power, in order to enable all sentient beings to attain faith and understanding and enter the ground of all-knowledge together. Therefore, one should know that such mudrās are born of faith and understanding in the Buddha. One should know that such mudrās are the emblems of the bodhisattvas. That is, using this upāya to reveal the Tathāgata's innerly realized virtues is why they are called "emblems." As for mudrās being manifold, even to the extent that bodily movements and postures are all mudrās: if the ācārya clearly understands yoga, deeply penetrates the esoteric purport, and can purify the bodhicitta—because through pure mind he thoroughly comprehends the esoteric Dharma—whatever he does is for the benefit and pacification of sentient beings, and whatever he carries out accords without exception with the Buddha's deportment. Therefore, of all bodily movements and actions, there is none that is not a mudrā. How could it be merely the karma of the body? Even all speech is likewise entirely mantra.