妙法蓮華經玄義 7.120

7.120

如此等壽三義，皆迹中因果之壽，此壽皆從本地因果圓滿而垂此迹，迹既如此，況復本也！經「我本行菩薩道時所成壽命，今猶未盡」，指於本因，因壽尚未盡，況本果壽！若執迹則不知本，今拂迹則識本，亦識不思議一也。

The three meanings of lifespans such as these are all lifespans of cause and effect within the traces. These lifespans are all traces manifested from the consummation of cause and effect in the original ground. If the traces are already like this, how much more so the original source! The sūtra states: 'The lifespan I attained when originally practicing the bodhisattva path is not even yet exhausted.' This points to the original cause; if the causal lifespan is not yet exhausted, how much more so the fruit-lifespan of the original source! If one clings to the traces, one does not know the original source; now, by brushing aside the traces, one recognizes the original source and also recognizes the inconceivable oneness.