首楞嚴義疏注經 9.59

9.59

「阿難！此四勝流，一切世間諸苦、樂境所不能動，雖非無為真不動地，有所得心功用純熟，名為四禪。」

"Ānanda, these four superior currents cannot be moved by any mundane states of suffering or bliss. Although this is not the unconditioned, true unshakable ground, because their mind of attainment has brought effort to full maturity, it is called the fourth dhyāna."