Valmiki Ramayana Yuddha Kanda Sarga 70 Shloka 59

वेगवान् endowed with speed, शैलनिकाशरूपः of mountain like form, सः he, वानरवीरमुख्यः chief of Vanaras, वेगवत् quickly, अभ्युपेत्य getting up, मुष्टिम् fist, सम्वर्त्य duly, तंराक्षसम् that Rakshasa, बाह्वन्तरे space between two arms, सहसा forcibly, जघान hit.

The chief of the Vanaras, whose form was like a mountain, endowed with speed, got up quickly, duly, and forcibly hit the Rakshasa (Mahaparsva) in the space between his arms.