Yoga sutra 1.18
Consciousness without object is when all activities and disruptions in the mind cease, in the highest samadhi/the highest state of spiritual absorption.
In the lower levels of samadhi (see yoga sutra 1.17) you are aware of three things: yourself as a meditator, the object of meditation, and the process of meditation. By contrast, in this sutra the highest level of spiritual absorption is explained, albeit there are no words than can truly describe the same.
In the highest level of spiritual absorption, there is no division/no separate awareness of yourself as a meditator, the object of meditation, and the process of meditation; all is one. All activities and disruptions in the mind cease and the mind stands so still that even traces of past experience no longer has any influence. This perfect stillness of mind defines this state of samadhi. The yogi is free from karma. The next sutra explains how to get there.
Damian Cadman-Jones is an authorised teacher of Prana Vashya Yoga™