Valmiki Ramayana Bala Kanda Sarga 46 Shloka 5
Original Shlokaएवं भवतु, भद्रं ते शुचिर्भव तपोधने। जनयिष्यसि पुत्रं त्वं शक्रहन्तारमाहवे।।1.46.5।।
1 source checked for this shloka
तपोधने O One having austerities as wealth, एवं भवतु 'Be it so', ते भद्रम् prosperity to you, शुचि: भव become pure, त्वम् you, आहवे in the battle, शक्रहन्तारम् slayer of Indra, पुत्रम् son, जनयिष्यसि will give birth.
"O one vested with the wealth of austerities be it so. Prosperity to you Remain chaste, you will deliver a son who will kill Indra in the battle.