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.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
श्रीशुक उवाच । इति मन्त्रोपनिषदं व्याहरन्तं समाहितम् । दृष्ट्वासुरा यातुधाना जग्धुमभ्यद्रवन् क्षुधा
śrīśuka uvāca | iti mantropaniṣadaṃ vyāharantaṃ samāhitam | dṛṣṭvāsurā yātudhānā jagdhumabhyadravan kṣudhā
SB 8.1.17