大乘起信論義記 3.216

3.216

問：若據此義，乃是眾生自心之中真如之用。云何說言佛報化耶？答：眾生真心即諸佛體更無差別，故《華嚴經》云「若人欲求知，三世一切佛，應當如是觀，心造諸如來。」又《不增不減經》云「法身即眾生，眾生即法身，法身與眾生，義一名異也。」既從法身起報化用，何得不是眾生真心耶？

Question: If based on this meaning, it is then the function of tathatā within the sentient beings' own mind. Why is it said to be the Buddha's reward and transformation [bodies]? Answer: The true mind of sentient beings is precisely the substance of all Buddhas, without any distinction. Hence the Avataṃsaka Sūtra states: "If one wishes to know / all the Buddhas of the three times, / one should contemplate thus: / the mind creates all Tathāgatas." Also the Anūnatvāpūrṇatvanirdeśa states: "The dharmakāya is precisely sentient beings, and sentient beings are precisely the dharmakāya; the dharmakāya and sentient beings are one in meaning and different in name." Since the functions of reward and transformation arise from the dharmakāya, how could it not be the true mind of sentient beings?