“Pratyahara is abstraction. It is the withdrawal of the senses from the objects. The senses are assimilated in the mind which is rendered pure through the practice of Yama, Niyama and Pranayama. The mind becomes more calm now. The nature of the senses is to have always connection with the objects. Where the vision is turned outward, the rush of fleeting events engages the mind. The outgoing energies of the mind begin to play. When they are obstructed by the practice of Pratyahara, the other course for them is to mix with the mind and to absorbed in the mind. The mind will not assume any form of any object. It will be ultimately merged in the Self within.
Pratyahara itself is termed as Yoga, as it is the most important Anga in Yoga Sadhana. This is the fifth rung in the Yogic ladder. The first four rungs deal with ethical training and purification of body, mind and Nadis. Now with Pratyahara, proper Yoga begins which eventually culminates in Dharana, Dhyana and finally in Samadhi.
He who has practised Pratyahara can have good concentration and meditation. His mind is always peaceful. This demands patience and constant practice. It takes some years before one is well-established in Pratyahara. He who has mastery over Pratyahara will never complain of Vikshepa or distraction of mind. He can sit in a place in a busy city where four roads meet and meditate whenever he likes. He does not want a cave for meditation. Just as the tortoise draws in on all sides its limbs, so also, the Yogi withdraws all his senses from the objects of sense through the practice of Pratyahara. Pratyahara gives power to the practitioner.”
Sadhana by Swami Sivananda
Yoga Sadhana: Its Eight Fundamentals – page 364