法華義疏 8.288

8.288

「佛說是經於八千劫」者，第三明說經時節。以其文廣是故時長，所以下云「說是《法華經》如恒河沙偈」也。

"The Buddha expounded this sūtra for eight thousand kalpas" is the third [part], clarifying the duration of expounding the sūtra. Because its text was extensive, the time was therefore long; hence it says below, "He expounded this Lotus Sūtra in verses numerous as the sands of the Ganges."