維摩經玄疏 1.153

1.153

一者、世間禪定不可說者，若初禪內有覺觀，猶是可說；二禪已上，無覺無觀，是不可說。

First is the ineffable of worldly dhyāna: within the first dhyāna there are coarse and subtle examination, so it is still effable; from the second dhyāna upward, there is neither coarse nor subtle examination, so it is ineffable.