सर्वभूतानि कौन्तेय प्रकृतिं यान्ति मामिकाम्। कल्पक्षये पुनस्तानि कल्पादौ विसृजाम्यहम् ॥

sarva-bhūtāni kaunteya prakṛitiṁ yānti māmikām kalpa-kṣhaye punas tāni kalpādau visṛijāmyaham

All beings, O Kaunteya, enter my lower nature at the end of a world-age; at the beginning of a world-age again I emanate them.

In plain words: Krishna tells Arjuna (called Kaunteya, "son of Kunti") that at the end of each great age of the universe, all beings sink back into his nature. When a new age begins, he sends them out again.