The above quote is the Mahavairocana Buddha speaking to the Bodhisattva Vajradhara in the first chapter of the Mahavairocana Sutra.
(Mahavairocana Sutra, page 3, translated by Chikyo Yamamoto of Koyasan University, published by the International Academy of Indian Culture and Aditya Prakashan of New Delhi, first published in 1990, reprinted in 2001.)