瑜伽論記 4.336

4.336

言以修悲者樂欲拔苦。無色界中遠離眾苦，斷壞等苦，彼都無故者，空處都無因色所生斷壞等苦。修悲心者，念苦眾生令到無苦及所依處，所依處是空處定無有眾苦，故言修悲極於空處。

Regarding the words: "Because one who cultivates compassion aspires to eradicate suffering. In the formless realm, one is far removed from the manifold sufferings; because sufferings such as disruption and destruction are completely absent there": in the sphere of infinite space, sufferings such as disruption and destruction produced on the basis of form are completely absent. One cultivating the compassionate mind reflects on suffering sentient beings, wishing to bring them to the state without suffering and to its support. That support is the concentration of the sphere of infinite space, where there are no manifold sufferings; hence it says that cultivating compassion reaches its peak at the sphere of infinite space.