Prabhupāda: The snakes, kāla-sarpa, indriya. Prabodhānanda Sarasvatī has explained about these kāla-sarpas, snake . . . our senses are compared with the snakes. Just like a snake, as soon as it touches somebody, it kills. It is very dangerous, touching by the lip of the snake. Similarly, a, a slight sense gratification is so dangerous, kāla-sarpa indriya-paṭalī, especially in the sex matter. So one . . . yogīs, they are training the senses how to restrain them from sense gratification, but a devotee, on account of their senses being engaged in the service of the Lord, there is no poisonous effect of the senses.
Hṛṣīkeṇa hṛṣīkeśa-sevanaṁ bhaktir ucyate (CC Madhya 19.170). Kṛṣṇa's another name is Hṛṣīkeśa. Rathaṁ sthāpaya acyuta. Hṛṣīkeśa. In the Bhagavad-gītā, this word is used, hṛṣīkeśa. So hṛṣīkeśa means "the master of the senses." Actually, our senses are given by Kṛṣṇa. We wanted a type of instrument to enjoy certain type of material enjoyment, and Kṛṣṇa has given us senses. Actually, the proprietor of the senses is Kṛṣṇa; therefore His name is Hṛṣīkeśa, "Master of the senses."
So if we actually use the senses for the service of the proprietor of the senses, that is bhakti.