瑜伽論記 23.219

23.219

自下第二明四種空所依，當知四行為所依止，第一、外空，以第二住內空心增上力故得初禪定，離生喜樂滋潤其身為所依止，及遍知我慢所恃所陵空故住於外空；第二、內空，即以第三於內外法修空無我見為所依止；第三、無我見，即以於彼修無常見為所依止，無常見以聞正法，如理作意為所依止。

From here, the second part clarifies the four bases of emptiness; one should know that the four practices are the bases: first, external emptiness takes as its basis the attainment of the concentration of the first dhyāna through the predominant power of the mind dwelling in the second, internal emptiness, so that the joy and pleasure born of seclusion permeate the body, as well as dwelling in external emptiness because of thoroughly knowing the emptiness of what is relied upon and arrogated by the pride of 'I'; second, internal emptiness takes the third practice—cultivating the view of emptiness and selflessness regarding internal and external phenomena—as its basis; third, the view of selflessness takes cultivating the view of impermanence toward them as its basis; the view of impermanence takes hearing the true Dharma and proper mental attention as its basis.