瑜伽論記 17.422

17.422

釋初數門中，答意，立四靜慮為超苦樂，初禪超憂，二禪離苦，三禪離喜，四禪離樂。若不至四離苦樂不盡，若其過四，是則無用，為是義故，但立於四不增不減。

In explaining the first gateway of numbers, the intention of the answer is that the four dhyānas are established to transcend suffering and pleasure: the first dhyāna transcends distress, the second dhyāna departs from suffering, the third dhyāna departs from joy, and the fourth dhyāna departs from pleasure. If one does not reach the fourth, one does not completely depart from suffering and pleasure; if one exceeds the fourth, it is useless. For this meaning, only four are established, neither increasing nor decreasing.