仁王護國般若波羅蜜多經疏 2.20

2.20

解曰：從麁至細，轉折明空。諸有為法漂馳不住，過去已無、未來當無，現在一念勿謂實有。拆此一念有九十剎那，勿謂剎那而有實體。拆一剎那有九百生滅，以多生滅成一剎那，剎那無體；以多剎那合成一念，念無實體，故說諸法念念皆空。

The commentary states: Proceeding from the coarse to the subtle, it clarifies emptiness step by step. All conditioned phenomena drift and gallop without abiding; the past is already non-existent, the future will be non-existent, and the present thought-moment must not be considered truly existent. Breaking down this single thought-moment, there are ninety kṣaṇas; do not consider a kṣaṇa to have a real substance. Breaking down a single kṣaṇa, there are nine hundred arisings and ceasings. Since a single kṣaṇa is constituted of many arisings and ceasings, the kṣaṇa is without substance; since a single thought-moment is composed of many kṣaṇas, the thought-moment is without real substance. Therefore, it is said that all phenomena are empty thought-moment by thought-moment.