SB 2.7.12
matsyo yuganta-samaye manunopalabdhah
ksonimayo nikhila-jiva-nikaya-ketah
visramsitan uru-bhaye salile mukhan me
adaya tatra vijahara ha veda-margan
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
At the end of the millennium, the would-be Vaivasvata Manu, of the name Satyavrata, would see that the Lord in the fish incarnation is the shelter of all kinds of living entities, up to those in the earthly planets. Because of my fear of the vast water at the end of the millennium, the Vedas come out of my [Brahma’s] mouth, and the Lord enjoys those vast waters and protects the Vedas.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
During one day of Brahma there are fourteen Manus, and at the end of each Manu there is devastation up to the earthly planets, and the vast water is fearful even to Brahma. So in the beginning of the would-be Vaivasvata Manu, such devastation would be seen by him. There would be many other incidents also, such as the killing of the famous Sankhasura. This foretelling is by the past experience of Brahmaji, who knew that in that fearful devastating scene the Vedas would come out of his mouth but the Lord in His fish incarnation not only would save all living entities, namely the demigods, animals, men and great sages, but would also save the Vedas.