In days of yore, the snakes were destroyed in the sacrifice of Janamejaya, but the terrified snakes were saved by a Brahmana.
जनमेजयस्य यज्ञेऽस्मिन् सर्पाणां हिंसनं पुरा। परित्राणां च भीतानां सर्पाणां ब्राह्मणादपि॥