The mind is both the instrument of enlightenment and the greatest obstacle to enlightenment. Both.
Without the mind, we do not sense anything. So, to be able to “see” and understand what we truly are, we need the mind. In this way, the mind is the instrument of enlightenment.
But the mind, if untrained and unpurified, is out of control and doesn’t perceive clearly.
Trying to have Self-Realization with such a mind is like trying to watch a movie on a malfunctioning television set, which constantly changes channels and is dark and blurry. How can you enjoy the movie? The untrained and unpurified mind jumps from thought to thought and distorts every perception. Such a mind is not able to grasp, let alone understand, the great Truth hidden within.
Thus, to reach enlightenment, we need to train the mind to be calm and steady, and also, we need to remove impurities from the mind that cause it to be dark and to distort what it perceives. The practices of Yoga are such a training course.