Valmiki Ramayana Bala Kanda Sarga 55 Shloka 1

तत: thereafter, वसिष्ठ: Vasishta, विश्वामित्रास्त्रमोहितान् stupefied by weapons of Visvamitra, आकुलान् agitated, तान् them, दृष्ट्वा having seen, कामधुक् O Kamadhenu, योगत: through yogic power, सृज create, चोदयामास thus he directed.

Thereafter, Vasishta having seen the forces tortured and overpowered by the weapons of Viswamitra said, "O Kamadhenu create additional forces through your yogic power." Viswamitra's sons and soldiers get destroyed in the clash--Viswamitra performs austerities and acquires divine weapons by pleasing Lord Siva.