Valmiki Ramayana Aranya Kanda Sarga 11 Shloka 11
Original Shlokaइदं पञ्चाप्सरो नाम तटाकं सार्वकालिकम्।।3.11.11।। निर्मितं तपसा राम मुनिना माण्डकर्णिना।
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राम O Rama, इदम् this, माण्डकर्णिना by Mandakarni, मुनिना by sage, तपसा through penance, निर्मितम् is created, सार्वकालिकम् for all times (to be filled with water), पञ्चाप्सरः नाम by name Panchapsara, तटाकम् lake.
O Rama this lake called Panchapsara filled with water at all times has been created through penance by a sage called Mandakarni.