Srimad-Bhagavatam: Canto 10 - Chapter 1 - Verse 41
केदारेभ्यस्त्वपोऽगृह्णन् कर्षका दृढसेतुभि: ।यथा प्राणै: स्रवज्ज्ञानं तन्निरोधेन योगिन: ॥ ४१ ॥
kedārebhyas tv apo ’gṛhṇankarṣakā dṛḍha-setubhiḥyathā prāṇaiḥ sravaj jñānaṁtan-nirodhena yoginaḥ
In the same way that the practitioners of yoga bring their senses under strict control to check their consciousness from flowing out through the agitated senses, the farmers erected strong mud banks to keep the water within their rice fields from draining out.
Śrīla Prabhupāda comments: “In autumn, farmers save the water within the fields by building strong walls so that the water contained within the field cannot run out. There is hardly any hope for new rainfall; therefore they want to save whatever is in the field. Similarly, a person who is actually advanced in self-realization protects his energy by controlling the senses. It is advised that after the age of fifty one should retire from family life and conserve the energy of the body for utilization in the advancement of Kṛṣṇa consciousness. Unless one is able to control the senses and engage them in the transcendental loving service of Mukunda, there is no possibility of salvation.”