Valmiki Ramayana Yuddha Kanda Sarga 31 Shloka 21
Original Shlokaतत्प्रहस्तप्रणीतेनबलेनमहतामम । बलमस्यहतंरात्रौयत्ररामस्सलक्ष्मणः ।।6.31.21।।
1 source checked for this shloka
सलक्ष्मणः that Lakshmana, रामः Rama, यत्र where in, प्रहस्तप्रणीतेन led by Prahastha, महता great, ममबलेन by my army, अस्य their, बलम् powerful, रात्रौ in the night, हतम् slayed.
"There in that camp Lakshmana and Rama are killed by my powerful army led by Prahastha at night."