Valmiki Ramayana Kishkindha Kanda Sarga 7 Shloka 4
Original Shlokaरावणं सगणं हत्वा परितोष्यात्मपौरुषम्। तथाऽस्मि कर्ता न चिराद्यथा प्रीतो भविष्यसि4.7.4।।
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सगणम् including clan, रावणम् Ravana, हत्वा after killing, आत्मपौरुषम् my prowess, परितोष्य satisfy, यथा as, प्रीतः pleased, भविष्यसि you will be, तथा that way, न चिरात् very soon, कर्तास्मि I will do
'With all my capability I will kill Ravana and his clan. Thus I will be able to satisfy you soon with my efforts.