As the spider sends forth and draws in its thread, as plants grow on the earth, as from every man hairs spring forth on the head and the body, thus does everything arise here from the Indestructible.

In plain words: A spider spins out its thread and takes it back in. Plants grow from the earth, and hair grows on a person's body. In the same natural way, everything in the world comes out of the Indestructible, Brahman.