大般涅槃經集解 9.144

9.144

案僧亮曰：凡夫受報色心，必須直以想微。二乘不知，名為無想天耳。有漏近事非汝境界，況無漏乎？僧宗曰：依此經所明，乃至四空斯皆有色。今無想天，是等四禪中四凡夫天之最上，那含天之下，有此一地。雖有色身，以其心細而無色想，唯佛乃知，餘無能了。

Sengliang comments: The physical and mental retributions of ordinary people must simply have subtle thoughts. Because the two vehicles do not know them, it is merely called the heaven of thoughtlessness. If an immediate matter with outflows is not your domain, how much less so the outflow-free? Sengzong comments: According to what this sūtra clarifies, even the four formless realms all have form. Now the heaven of thoughtlessness is the highest of the four ordinary heavens among the fourth dhyāna; below the anāgāmin heaven, there is this ground. Although they have a physical form, because their minds are subtle and they have no thoughts of form, only the Buddha knows this, and no others can comprehend it.