大乘起信論裂網疏 5.99

5.99

問：既云無所不在，則初二三禪亦可成佛，何必定在色究竟天？答：此有二義：一者《華嚴》明第十地菩薩位寄四禪，即於此處示成佛故；二者將成佛時，所入金剛喻定，必依捨俱禪故。

Question: Since it is said to be nowhere not present, Buddhahood could also be attained in the first, second, or third dhyānas; why must it be specifically in the Akaniṣṭha Heaven? Answer: There are two meanings to this: first, the Avataṃsaka clarifies that the position of a bodhisattva on the tenth ground is lodged in the fourth dhyāna, and it is right there that they manifest the attainment of Buddhahood; second, when on the verge of attaining Buddhahood, the vajropamasamādhi entered must rely on dhyāna accompanied by equanimity.