Shatapatha Brahmana 3.5.1.21

3.5.1.21

tebhyo ha vākcukrodha | kena madeṣa śreyānbandhunā kenā yadetam pratyagrahīṣṭa na māmiti sā haibhyo 'pacakrāma sobhayānantareṇa devāsurāntsayattāntsiṃhī bhūtvādadānā cacāra tāmupaiva devā amantrayantopāsurā agnireva devānāṃ dūta āsa saharakṣā ityasurarakṣasamasurāṇām

Now Vâk was angry with them: 'In what respect, forsooth, is that one better than I,--wherefore is it, that they should have accepted him and not me?' So saying she went away from them. Having become a lioness she went on seizing upon (everything) between those two contending parties, the gods and the Asuras. The gods called her to them, and so did the Asuras. Agni was the messenger of the gods, and one Saharakshas for the Asura-Rakshas.