Sefer HaBahir 2

1Rabbi Berechiah said, "It is written, 'Now the earth was tohu and bohu' (Genesis 1:2). What does 'was' mean? That the tohu already was. What is tohu? Something that confounds [m'taha] people. And what is bohu? Tohu was, and it returned to bohu. And what is bohu? A thing that has substance in it, as is written, 'It is inside it [bo hu].'"