SB 1.10 - The Lord exists before creation and after dissolution
The ladies of Hastināpura speaking with reverence in śānta rati said that Kṛṣṇa is the Original Person (puruṣa purātanaḥ), who alone existed before the material creation, and in whom all living beings merge at the time of dissolution. There are two types of dissolution of the cosmos: one at the end of Brahmā’s day (4,320,000,000 years) and the other at the end of Brahmā’s life (8,640,000,000 x 30 x 12 x 100 years). In both periods both the material energy called the mahat-tattva and the marginal energy called jīva-tattva merge in the person of the Lord. The living beings remain asleep, their energy suspended, in the body of the Lord until there is another creation of the material world. The living entities do not lose their identities when they are merged in the body of the Lord, for they awaken when there is another creation. The Lord alone exists in His svarūpa at the time of dissolution and no others.
The material creation is effected by the interaction of the three modes of material nature set in action by the Lord, who existed before the modes were set into motion. Thus the Lord is not a product of the material energy and His body is completely spiritual. In the Śruti it is said only Mahā-Viṣṇu existed before creation and by His breathing all the universes are generated in seeds and gradually develop into gigantic forms. This Mahā-Viṣṇu is the plenary portion of Kṛṣṇa. The ladies must have heard all these truths from authoritative sources like Vyāsa.