Valmiki Ramayana Bala Kanda Sarga 24 Shloka 1

तत: thereafter, अरिन्दमौ two destroyers of enemies, विमले on a pure, प्रभाते daybreak, कृताह्निकम् by observing daily oblations, विश्वामित्रम् Viswamitra, पुरस्कृत्य ahead of them नद्या: river's, तीरम् bank, उपागतौ arrived.

Thereafter the destroyers of foes, Rama and Lakshmana offering their morning oblations on that bright dawn arrived at the bank of the river (Ganga) with Viswamitra ahead of them. While crossing the river Rama asks "What is this tumultuous sound gushing from the Ganga?"--Viswamitra gives the reply--The trio enter the forest -- Viswamitra narrates the story of Tataka.