SB 8.1.17

śrī-śuka uvāca
iti mantropaniṣadaṁ
 vyāharantaṁ samāhitam
dṛṣṭvāsurā yātudhānā
 jagdhum abhyadravan kṣudhā
Synonyms: 
śrī-śukaḥ uvāca — Śrī Śukadeva Gosvāmī said; iti — thus; mantra-upaniṣadam — the Vedic mantra (uttered by Svāyambhuva Manu); vyāharantam — taught or chanted; samāhitam — concentrated the mind (without being agitated by material conditions); dṛṣṭvā — upon seeing (him); asurāḥ — the demons; yātudhānāḥ — the Rākṣasas; jagdhum — desired to devour; abhyadravan — running very fast; kṣudhā — to satisfy their appetite.
Translation: 
Śukadeva Gosvāmī continued: Svāyambhuva Manu was thus in a trance, chanting the mantras of Vedic instruction known as the Upaniṣads. Upon seeing him, the Rākṣasas and asuras, being very hungry, wanted to devour him. Therefore they ran after him with great speed.