Mbh 1.76.4a

“Between the celestials and the Asuras, there happened, of yore, frequent encounters for the sovereignty of the three worlds with everything in them. The gods, then, from desire of victory, installed the son of Angiras (Vrihaspati) as their priest to conduct their sacrifices; while their opponents installed the learned Usanas as their priest for the same purpose. And between those two Brahmanas there are always much boastful rivalry. Those Danavas assembled for encounter that were slain by the gods were all revived by the seer Sukra by the power of his knowledge. And then starting again, into life,--these fought with the gods. The Asuras also slew on the field of battle many of the celestials. But the open-minded Vrihaspati could not revive them, because he knew not the science called Sanjivani (re-vivification) which Kavya endued with great energy knew so well. And the gods were, therefore, in great sorrow. And the gods, in great anxiety of heart and entertaining a fear of the learned Usanas, then went to Kacha, the eldest son of Vrihaspati, and spoke unto him, saying, ‘We pay court to thee, be kind to us and do us a service that we regard as very great. That knowledge which resides in Sukra, that Brahmana of immeasurable prowess, make thy own as soon as thou canst. Thou shalt find the Brahmana in the court of Vrishaparvan. He always protects the Danavas but never us, their opponents. Thou art his junior in age, and, therefore, capable of adoring him with reverence. Thou canst also adore Devayani, the favourite daughter of that high-souled Brahmana. Indeed, thou alone art capable of propitiating them both by worship. There is none else that can do so. By gratifying Devayani with thy conduct, liberality, sweetness, and general behaviour, thou canst certainly obtain that knowledge.’ The son of Vrihaspati, thus solicited by the gods, said ‘So be it, and went to where Vrishaparvan was.