SB 8.1.17
sri-suka uvaca
iti mantropanisadam
vyaharantam samahitam
drstvasura yatudhana
jagdhum abhyadravan ksudha
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Sukadeva Gosvami continued: Svayambhuva Manu was thus in a trance, chanting the mantras of Vedic instruction known as the Upanisads. Upon seeing him, the Raksasas and asuras, being very hungry, wanted to devour him. Therefore they ran after him with great speed.