大乘起信論裂網疏 4.77

4.77

"Furthermore, the function of tathatā: this means that when all Buddhas were on the causal stage, they generated great compassion, practiced the various perfections, the four means of embrace, and other practices, viewed beings as equal to themselves, universally delivered them all, to the end of future limits without restriction of kalpas, truly knew the equality of self and other, and yet did not grasp at the marks of sentient beings. With such wisdom of great skillful means, they extinguished beginningless ignorance, realized the fundamental Dharmakāya, and spontaneously gave rise to various autonomous and differentiated activities of inconceivable karma, whose functioning pervades the dharmadhātu, being coextensive with tathatā, and yet no mark of function can be apprehended. Why? Because all Tathāgatas are solely the ultimate truth of the Dharmakāya, without any functioning within the realm of conventional truth."