Valmiki Ramayana Ayodhya Kanda Sarga 23 Shloka 23
Original Shlokaअहं तदाशां छेत्स्यामि पितुस्तस्याश्च या तव। अभिषेकविघातेन पुत्रराज्याय वर्तते।।2.23.23।।
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तत् for that reason, अहम् I, पितुः father's, या Kaikeyi, तव your, अभिषेकविघातेन by obstructing your consecration, पुत्रराज्याय the kingdom for her son, वर्तते is intending, तस्याश्च her, आशाम् desire, छेत्स्यामि I will break asunder.
Therefore, I shall frustrate the desire of father and of Kaikeyi who plans the kingdom for her son by obstructing your consecration.