成唯識論述記 2.385

2.385

述曰：第六、體等相同難。又所相法三世恒有，而言有生等來與法合，汝之無為體恒有，應有生等合，以此返成無為無生等，有為亦應然，此中比量返覆可知。

The Commentary states: Sixth is the objection that their substances are identical. Furthermore, what is marked is constantly existent throughout the three times, yet you say that birth and the others come to combine with the phenomenon; your unconditioned phenomenon is constantly existent in substance, so it should combine with birth and the others. By using this to establish in turn that the unconditioned has no birth and the others, the conditioned should also be like this; the syllogisms here are known by inversion.