Valmiki Ramayana Ayodhya Kanda Sarga 18 Shloka 34
Original Shlokaयदि सत्यप्रतिज्ञं त्वं पितरं कर्तुमिच्छसि। आत्मानं च नरश्रेष्ठ मम वाक्यमिदं शृणु।।2.18.34।।
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नरश्रेष्ठ O best among men, त्वम् you, पितरम् your father, आत्मानं च yourself as well, सत्यप्रतिज्ञम् truthful to promise, कर्तुम् to make, इच्छसि यदि if you want, मम my, इदं वाक्यम् these words, शृणु listen.
O the best of men if you want to be true to the word given by you and your father, listen to what I say.