MN 1:18.1–18.4

Nevasaññānāsaññāyatanaṁ nevasaññānāsaññāyatanato sañjānāti; nevasaññānāsaññāyatanaṁ nevasaññānāsaññāyatanato saññatvā nevasaññānāsaññāyatanaṁ maññati, nevasaññānāsaññāyatanasmiṁ maññati, nevasaññānāsaññāyatanato maññati, nevasaññānāsaññāyatanaṁ meti maññati, nevasaññānāsaññāyatanaṁ abhinandati. Taṁ kissa hetu? ‘Apariññātaṁ tassā’ti vadāmi.

They perceive the dimension of neither perception nor non-perception as the dimension of neither perception nor non-perception. Having perceived the dimension of neither perception nor non-perception as the dimension of neither perception nor non-perception, they conceive it to be the dimension of neither perception nor non-perception … Why is that? Because they haven’t completely understood it, I say.