大毘盧遮那成佛經疏 10.83

10.83

次地神真言。地能持萬物，一切萬物依之生長，當知即是佛心。猶如來心能持萬物，深入持本三昧而說真言也。亦是釋迦方便化身耳。

Next is the mantra of the Earth Deity. The earth can sustain all things, and all things depend upon it for growth; one should know that this is none other than the Buddha Mind. Just as the Tathāgata's mind can sustain all things, she deeply enters the sustaining-the-origin samādhi and speaks the mantra. She is also simply an upāya emanation body of Śākyamuni.