成唯識論述記 4.201

4.201

述曰：下出別理。起染淨法不熏成種，所起唐捐，空無果故。唐之言虛，捐之言棄也。生死、涅槃無由斷、得，故無生死亦無涅槃。

The Commentary states: Below sets forth the specific reason. When defiled and pure dharmas arise, if they do not perfume and form seeds, what arises would be in vain, being empty without fruit. 'Tang' (fruitless) means empty; 'juan' (lose) means abandoned. Saṃsāra and nirvāṇa would have no cause for termination or attainment, and thus there would be neither saṃsāra nor nirvāṇa.