大般涅槃經義記 8.134

8.134

四約人分別，凡、佛雖殊，體性無別。體無別故，將凡取性，性名為因；據佛取性，性即佛果。故上宣說苦、集等實即是如來，是佛果故名為智慧。

Fourth, discriminating in terms of persons: although ordinary beings and buddhas differ, their essential nature is without distinction. Because the essence is without distinction, taking the nature with reference to ordinary beings, the nature is named the cause; taking the nature on the basis of the Buddha, the nature is precisely the fruit of buddhahood. Therefore, it was proclaimed above that the realities of suffering, origin, and so forth are precisely the Tathāgata; because it is the fruit of buddhahood, it is named wisdom.