法華義疏 7.112

7.112

「我雖年朽由故貪惜」者，第三、明老年見子，喜之甚也。財物於老年無用而貪惜為子，教法於佛乃無用，貪惜為於眾生也。

As for "although I am decrepit with age, I still cherish and begrudge it," third, this explains seeing the son in old age, rejoicing exceedingly. Wealth and goods are of no use in old age, but he cherishes and begrudges them for his son; teachings are of no use to the Buddha, but he cherishes and begrudges them for sentient beings.