SB 10.3.25

naṣṭe loke dvi-parārdhāvasāne
 mahā-bhūteṣv ādi-bhūtaṁ gateṣu
vyakte ’vyaktaṁ kāla-vegena yāte
 bhavān ekaḥ śiṣyate ’śeṣa-saṁjñaḥ
Synonyms: 
naṣṭe — after the annihilation; loke — of the cosmic manifestation; dvi-parārdha-avasāne — after millions and millions of years (the life of Brahmā); mahā-bhūteṣu — when the five primary elements (earth, water, fire, air and ether); ādi-bhūtam gateṣu — enter within the subtle elements of sense perception; vyakte — when everything manifested; avyaktam — into the unmanifested; kāla-vegena — by the force of time; yāte — enters; bhavān — Your Lordship; ekaḥ — only one; śiṣyate — remains; aśeṣa-saṁjñaḥ — the same one with different names.
Translation: 
After millions of years, at the time of cosmic annihilation, when everything, manifested and unmanifested, is annihilated by the force of time, the five gross elements enter into the subtle conception, and the manifested categories enter into the unmanifested substance. At that time, You alone remain, and You are known as Ananta Śeṣa-nāga.
Purport: 

At the time of annihilation, the five gross elements — earth, water, fire, air and ether — enter into the mind, intelligence and false ego (ahaṅkāra), and the entire cosmic manifestation enters into the spiritual energy of the Supreme Personality of Godhead, who alone remains as the origin of everything. The Lord is therefore known as Śeṣa-nāga, as Ādi-puruṣa and by many other names.

Devakī therefore prayed, “After many millions of years, when Lord Brahmā comes to the end of his life, the annihilation of the cosmic manifestation takes place. At that time the five elements — namely earth, water, fire, air and ether — enter into the mahat-tattva. The mahat-tattva again enters, by the force of time, into the nonmanifested total material energy, the total material energy enters into the energetic pradhāna, and the pradhāna enters into You. Therefore after the annihilation of the whole cosmic manifestation, You alone remain with Your transcendental name, form, quality and paraphernalia.

“My Lord, I offer my respectful obeisances unto You because You are the director of the unmanifested total energy, and the ultimate reservoir of the material nature. My Lord, the whole cosmic manifestation is under the influence of time, beginning from the moment up to the duration of the year. All act under Your direction. You are the original director of everything and the reservoir of all potent energies.”