Valmiki Ramayana Bala Kanda Sarga 35 Shloka 1

विश्वामित्र: Visvamitra, रात्रिशेषम् rest of the night, महर्षिभि: with ascetics, शोणाकूले on the bank of river Sona, उपास्य waiting, निशायाम् in the night, सुप्रभातायाम् at dawn, अभ्यभाषत said.

Viswamitra lay on the bank of Sona with the ascetics, for the rest of the night. (Getting up) at daybreak he said: Viswamitra narrates the legend of sacred Ganga