金剛三昧經論 3.49

3.49

論曰：此是第二答。如來辯才無礙自在，故說一偈攝諸佛法。佛法之要在此四句，令鈍根者誦持一偈常念思惟，乃至遍知一切佛法，是名如來善巧方便。

The commentary states: This is the second part, the answer. The Tathāgata's eloquence is unobstructed and sovereign; therefore he speaks a single verse that subsumes all buddhadharmas. The essence of the buddhadharma lies in these four lines, causing those of dull faculties to recite and uphold a single verse, constantly mindful and contemplating it, up to comprehensively knowing all buddhadharmas—this is called the Tathāgata's skillful expedient.