Valmiki Ramayana Yuddha Kanda Sarga 78 Shloka 10
Original Shlokaअहंराक्षसराजेनरावणेनमहात्मना । आज्ञप्तःसमरेहन्तुंतावुभौरामलक्ष्मणौ ।।6.78.10।।
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अहम् I, राक्षसराजेन by Rakshasa king's, महात्मना great self, रावणेन to Ravana, समरे in battle, तौ those, रामलक्ष्मणौ Rama and Lakshmana, उभौ both, हन्तुम् will kill, आज्ञप्तः by his order
"I will kill both Rama and Lakshmana in the battle, by the order of Ravana, the king of Rakshasas."