Valmiki Ramayana Sundara Kanda Sarga 64 Shloka 29
Original Shlokaदृष्टा देवी न सन्देहो न चान्येन हनूमता।।5.64.29।। न ह्यन्यः कर्मणो हेतुस्साधनेऽस्य हनूमतः।
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कर्मणो this task, हेतुस्साधनेऽस्य the reason for accomplishing, देवी Sita, दृष्टा saw, सन्देहः doubt, न not, अन्येन not others, न not, हनुमता Hanuman.
"Hanuman is the one who has accomplished this task. Who else can? No doubt, he has seen Sita.