法華玄論 2.96

2.96

問：汝雖種種門說佛是常，此就道理明是常耳。而此經文佛口自說無常，不應違經明是常耶。如經云「復倍上數」，終有限極，故終是無常也。

Question: Although you explain through various approaches that the Buddha is permanent, this is only explaining permanence in terms of the principle. However, in the text of this scripture the Buddha's own mouth speaks of impermanence; one should not contradict the scripture to declare permanence. As the scripture says, "again twice the above number"; since there is ultimately a limit, it is ultimately impermanent.