大乘起信論義記 3.287

3.287

"How is this remedied? Because the tathāgatagarbha has no prior limit, the mark of avidyā is also without beginning. If one says that outside the three realms there are other sentient beings who first begin, that is the teaching of non-Buddhist scriptures. Furthermore, the tathāgatagarbha has no subsequent limit, and because the nirvāṇa attained by the Buddhas is conjoined with it, it is likewise without a subsequent limit."