妙法蓮華經文句 2.158

2.158

「佛所護念」者，無量義處是佛自所證得，是故如來之所護念。下文云：「佛自住大乘也，雖欲開示，眾生根鈍，久默斯要，不務速說。」故言護念。

Regarding "guarded and kept in mind by the buddhas": the locus of immeasurable meanings is what the Buddha has personally realized, and is therefore what the Tathāgatas guard and keep in mind. As the text below says: "The Buddha himself abides in the Mahāyāna; although wishing to open and reveal it, sentient beings' faculties are dull, so he long remained silent on this essential point and did not hasten to preach it quickly." Therefore it says "guarded and kept in mind."