Valmiki Ramayana Yuddha Kanda Sarga 122 Shloka 18
Original Shlokaइदानीं च विजानामियथासौम्य सुरेश्वरैः । वधार्थंरावणस्येहविहितंपुरुषोत्तम ।।6.122.18।।
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सौम्य gentle, पुरुषोत्तम excellent, इह here, रावणस्य Ravana's, वधार्थम् to kill him, सुरेश्वरैः by ruler of gods, यथा so, विहितम् for destruction, इदानीं च in this form, विजानामि I did not know
"O gentle son! I did not know that the ruler of gods had sent you for the destruction of Ravana, O excellent one."