俱舍論記 28.22

28.22

「諸等持內至獨名靜慮」者，答。八等持內唯此四種：一攝受靜慮支；二止、觀均行最能審慮；三得現法樂住；四得樂通行名。故四等持獨名靜慮，餘定不爾。

As for "Among all samādhis... are uniquely called dhyāna": this is the answer. Among the eight samādhis, only these four [are so called, because]: first, they possess the factors of dhyāna (dhyānāṅga); second, śamatha and vipaśyanā proceed equally in them so that they are most capable of deliberate investigation; third, they attain pleasant abiding in the present life (dṛṣṭadharmasukhavihāra); fourth, they obtain the name 'path of easy progress' (sukhā pratipad). Therefore, these four samādhis alone are called dhyāna, while the remaining concentrations are not.