Prabhupada's lecture - Śrīmad-Bhāgavatam 1.5.13 - New Vrindaban, June 13, 1969
Then pratyāhāra. Pratyāhāra means that your senses have been withdrawn from material engagement. The example is just like the tortoise. The tortoise can wind up all these parts of the limbs of the body within immediately. And when it is required, he can expand. So pratyāhāra means that you have to withdraw the sensual activities inside. When you withdraw your senses for inside activities, that is Kṛṣṇa consciousness. That is Kṛṣṇa consciousness. You have to think of always how to satisfy Kṛṣṇa. Hṛṣīkeṇa hṛṣīkeśa-sevanam [Cc. Madhya 19.170]. Therefore hṛṣīka, hṛṣīka means the senses, and hṛṣīkeśa means the master of the senses. Kṛṣṇa is the master of the senses. I am possessing my hand, but actually the owner of the hand is Kṛṣṇa. These things are very nicely explained in Bhagavad-gītā. Mattaḥ smṛtir jñānam apohanaṁ ca [Bg. 15.15].
Suppose you are writing with your hands. So your memory must be acting; otherwise you cannot write. If your memory, if your brain, does not act, how you can write? Suppose you are typing. If memory does not act, then what is the use of this hand or your leg? Then Bhagavad-gītā says, Kṛṣṇa says, sarvasya cāham hṛdi sanniviṣṭaḥ: "I am sitting in everyone's heart." Mattaḥ smṛtir jñānam: "The knowledge and memory is from Me." Therefore, when Kṛṣṇa gives you memorization, gives you knowledge, then you can write or do something.