首楞嚴義疏注經 2.38

2.38

生滅麁相如前可知，不生滅性亦在汝身，汝知之否。匿王舉外敘疑，俾欲世尊明示，今蒙佛問，故答不知。

The coarse characteristics of arising and ceasing can be known as described above; the nature of non-arising and non-ceasing is also within your body—do you know it or not? King Prasenajit had brought up external [views] to express his doubt, wanting the World-Honoured One to clearly reveal it; now, receiving the Buddha's question, he answers that he does not know.