The brāhmaṇas replied: O best of kings, the snake Takṣaka has not fallen into the fire because he is being protected by Indra, whom he has approached for shelter. Indra is holding him back from the fire.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
तं गोपायति राजेन्द्र शक्रः शरणमागतम् । तेन संस्तम्भितः सर्पस्तस्मान्नाग्नौ पतत्यसौ
taṃ gopāyati rājendra śakraḥ śaraṇamāgatam | tena saṃstambhitaḥ sarpastasmānnāgnau patatyasau
SB 12.6.19