रात्रौ युद्धप्रवृत्तिः — Night Battle Begins; Duryodhana’s Protective Orders for Droṇa
Droṇa-parva 139
संजय उवाच तान् निहत्य महाबाहू राधेयस्यैव पश्यतः । सिंहनादरवं घोरमसृजत् पाण्डुनन्दन:,संजय कहते हैं--राजन्! राधानन्दन कर्णके देखते-देखते उन सातों भाइयोंको मारकर पाण्डुनन्दन महाबाहु भीमने भयंकर सिंहनाद किया
sañjaya uvāca tān nihatyā mahābāhū rādheyasyaiva paśyataḥ | siṃhanāda-ravaṃ ghoraṃ asṛjat pāṇḍu-nandanaḥ ||
Sanjaya said: O King, after slaying those men right before Radheya Karna’s eyes, the mighty-armed son of Pandu—Bhima—let out a dreadful lion-roar, a cry of triumph meant to shake the enemy’s resolve and proclaim his prowess in the midst of war.
संजय उवाच
In the battlefield ethic of the Mahabharata, valor is not only physical but also psychological: a warrior’s siṃhanāda (lion-roar) functions as a declaration of fearlessness and a deliberate challenge meant to unsettle the opponent—here, directed pointedly at Karna as witness.
Bhima has just slain a group of foes (referred to as 'them') while Karna watches. Immediately afterward, Bhima roars like a lion—an emphatic signal of victory and intimidation amid the ongoing fighting in the Drona Parva.