俱舍論頌疏論本 20.38

20.38

無色通三界，各三淨識境者，無色所繫苦集修斷各十識緣，謂通三界，各三為九，三謂苦集修也。無漏淨識為十。此之十識一一皆容緣無色界苦集修斷。

As for 'For the formless realm, they extend across the three realms, with three each, and pure consciousness being their domains': what are bound to the formless realm and abandoned by suffering, origin, and cultivation are each taken as an object by ten consciousnesses; namely, extending across the three realms, with three from each making nine—the three being [those abandoned by seeing] suffering, origin, and cultivation. Uncontaminated pure consciousness makes the tenth. Each of these ten consciousnesses can take what are abandoned by suffering, origin, and cultivation in the formless realm as an object.