Srimad Bhagavatam Canto 08, Chapter 11, Text 37

SB 8.11.37

iti sakram visidantam
 aha vag asaririni
nayam suskair atho nardrair
 vadham arhati danavah
 
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
Sukadeva Gosvami continued: While the morose Indra was lamenting in this way, an ominous, unembodied voice said from the sky, “This demon Namuci is not to be annihilated by anything dry or moist.”
Srimad Bhagavatam Canto 08, Chapter 11, Text 36
Srimad Bhagavatam Canto 08, Chapter 11, Text 38