大毘盧遮那成佛經疏 13.19

13.19

*Dharmadhātu* is the realm of phenomena; the realm of phenomena is the body of the Buddha. The lower phrase says "I," meaning "I am precisely the dharmadhātu." Moreover, although this practitioner has not yet realized the true nature in substance, merely by forming this mudrā and reciting the mantra, his substance also becomes identical to the dharmadhātu. As for its mudrā: bend the two space fingers inside the palms, press them with the earth, water, and fire fingers of both left and right hands to form fists, and erect the two wind [fingers] straight (each hand separately forms a fist and erects the wind finger). First erect the two fingers together in front of the chest, then rotate them inward, causing the two fingers from both sides of the crown to approach the left and right cheeks and neck respectively, and draw them inward, pulling them slightly downward. That is to say, when first erecting the fingers, make the fingertips point slightly downward with the backs of the fingers inward; bringing them close to the head and cheeks, gradually lower the fingertips, and upon reaching the heart, release the hands. Whenever reciting mantras and forming mudrās, it is like two plowing oxen advancing together: neither may be ahead or behind.