Kāya-sakkhi: 'body-witness', is one of the 7 Noble Disciples see: ariya-puggala B.. He is one who in his own person lit. body has attained the 8 deliverances vimokkha, and after wisely understanding the phenomena, the fermentations have partly come to ceasing Pug. 32. In A. IX, 44 it is said: A monk, o brother, attains the 1st absorption Jhanas, and as far as this domain reaches,- so far he has realized it in his own person. Thus the Blessed One calls such a person a body-witness in certain respects. The same is then repeated with regard to the 7 higher absorptions. Further again, o brother, the Bhikkhu attains the ceasing of perception and feeling see: nirodha-samāpatti and after wisely understanding the phenomena, all the fermentations come to ceasing. Thus, o brother, the Blessed One calls such a person a body-witness in all respects.
Maha Thera Nyanatiloka. Manual of Buddhist Terms and Doctrines, Buddhist Publication Society, first edition 1952.