Valmiki Ramayana Sundara Kanda Sarga 64 Shloka 18
Original Shlokaतव चेदं सुसदृशं वाक्यं नान्यस्य कस्यचित्। सन्नतिर्हि तवाख्याति भविष्यच्छुभयोग्यताम्।।5.64.18।।
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इदं वाक्यम् these words, तव च you alone would have said, सुसदृशम् your humility, अन्यस्य in others, कस्यचित् you only, न not, तव your, सन्नतिः humble, भविष्यच्छुभयोग्यताम् fit for a bright future, आख्याति speaks of.
"You alone could speak such words. Your humility speaks of your fitness for a bright future.