大方廣圓覺修多羅了義經略疏 2.794

2.794

謂非但了知二乘涅槃為我相，設使了知如來涅槃亦是我相。然涅槃但是覺體，非別有可證。今既證得涅槃，不忘能所，即是我相。

This means that not only is comprehending the nirvāṇa of the two vehicles the mark of a self, but even if one comprehends the nirvāṇa of the Tathāgata, it is also the mark of a self. Yet nirvāṇa is simply the essence of enlightenment, not something separate that can be realized. Now, having attained the realization of nirvāṇa, if one does not forget subject and object, that is precisely the mark of a self.