Mahabharata 1.121.22

1.121.22

vaiśaṃpāyana uvāca |
tathetyuktvā tatastasmai prādādastrāṇi bhārgavaḥ |
sarahasyavrataṃ caiva dhanurvedamaśeṣataḥ || 22 ||

"Saying, 'So be it,' the son of Bhrigu gave all his weapons unto Drona,--indeed, the whole science of arms with its rules and mysteries. Accepting them all, and thinking himself amply rewarded that best of Brahmanas then, glad at heart, set out, for (the city of) his friend Drupada.'"