Valmiki Ramayana Bala Kanda Sarga 30 Shloka 5
Original Shlokaतौ तु तद्वचनं श्रुत्वा राजपुत्रौ यशस्विनौ। अनिद्रौ षडहोरात्रं तपोवनमरक्षताम्।।1.30.5।।
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यशस्विनौ the two illustrious, तौ राजपुत्रौ the two princes, तत् वचनम् those words, श्रुत्वा having heard, षडहोरात्रम् six days and six nights, अनिद्रौ without sleep, तपोवनम् Tapovana, अरक्षताम् protected.
At these words of the sages the illustrious princes got ready to protect the tapovana for six days and six nights without sleep.