It is the mind, which is the cause of bondage as well as freedom.
Consider the mind. When it gets involved in the three Gunas – when there is an upset in the balance of the three Gunas, then one of the Gunas becomes predominant and the Atman gets involved in the play of the emotions.
The mind turns away from the inner self and begins to be interested in the objects of the senses – it seeks gratification of them and it wanders farther and farther away from the Atman.
This same mind, if it is turned inwards, if it attaches itself to the Lord, then this same mind will be the cause of freedom of man from the coils of the senses. This path is called by the name Chittasanyamana and it is the first step towards Moksha.
(Source: Srimad Bhagavatam (Page 71 -72) 10th edition – Kamala Subramanian – Bharatiya Vidya Bhavan)