俱舍論頌疏論本 2.11

2.11

無色所繫唯後三種，所謂意界、意識界、法界。眼等五根、色等五境，此十是色，無色離色，故無此十。無此十故，五識亦無。故論云：「依緣無故，五識亦無（五根為依，五境為緣）。」故唯後三無色界繫。

Those bound to the formless realm are only the last three, namely the mind-dhātu, mental consciousness dhātu, and dharmadhātu. The five faculties such as the eye, and the five objects such as visible form—these ten are material. The formless realm is free from matter, and therefore lacks these ten. Because it lacks these ten, the five consciousnesses are also absent. Hence the treatise says: "Because their supports and conditions are absent, the five consciousnesses are also absent (the five faculties are the supports, and the five objects are the conditions)." Therefore only the last three are bound to the formless realm.