Karma Seeds Still Remain in the Tathāgatagarbha After an Arhat's Nirvāṇa

Because arhats have eradicated the grasping on self, they no longer grasp at the worldly dharmas of the three realms. When the ignorance of one thought has been extinguished, and when their conditions with the three realms come to an end, they enter nirvāṇa and will no longer be born within the three realms. As for the claim that arhats will in the future emerge from nirvāṇa, that is because they have been steeped in the Mahāyāna teachings, and the seeds of the Mahāyāna dharma have ripened in their conditions—not because the seeds of the dharmas of the three realms have ripened. Arhats will no longer be born in the three realms due to the seeds of the dharmas of the three realms.

Then, at the time an arhat enters nirvāṇa, do the seeds of the dharmas of the three realms still exist? A seed is the aspect of generative capacity; where there are seeds, they must necessarily manifest as current activity. Yet an arhat no longer manifests the seeds of the three realms—so where have the seeds of the three realms gone?

Seeds are formed because of ignorance and power of vows. An arhat's ignorance of one thought has been extinguished, so no more seeds of the three realms will be formed; and since the arhat has no power of vows, no seeds of the three realms will be formed either. According to the dharma of the twelve links of dependent origination, ignorance produces volitional formations, and these volitional formations are all the dharmas of bodily, verbal, and mental actions within the three realms. Without ignorance, the volitional formations of the three realms must all vanish, and there will be no further birth of a body of the five aggregates. The Mahāyāna teachings that an arhat was steeped in before entering nirvāṇa become seeds deposited in the mind-substance, and even their slight inclination of delight toward the Mahāyāna dharma also becomes a seed, capable of bringing about the ripening of the conditions for the Mahāyāna seeds. The greater the delight, the more easily the conditions ripen, and the earlier they ripen—the earlier, then, the arhat will emerge from the state of nirvāṇa and take rebirth once again.

Before an arhat enters nirvāṇa, because the manas no longer grasps, the seeds of the Mahāyāna dharma are stored in the USB drive (the tathāgatagarbha). When that arhat is reborn in a future life, it is the seeds in the USB drive (the tathāgatagarbha) that, upon ripening, summon forth the world of the five aggregates.