大乘百法明門論解 1.27

1.27

言三時者，初四阿含言有，第二時八部般若言空，第三時即解深密經空有雙彰，中道教也。

Regarding the three periods: in the first, the four Āgamas speak of existence; in the second period, the Prajñāpāramitā in eight sections speaks of emptiness; the third period is the Saṃdhinirmocana-sūtra, in which both emptiness and existence are displayed together: the teaching of the Middle Way.