Valmiki Ramayana Kishkindha Kanda Sarga 16 Shloka 21

एवम् in that way, उक्तः सुग्रीवः Sugriva having been addressed, क्रुद्धः angry, वालिनम् Vali, अब्रवीत् said, एषः thus, मुष्टिः fist, तव your, प्राणान् life, हरन् take, मूर्धनि on your forehead, पततु let it hit

This infuriated Sugriva who, looking at Vali, said 'This fist of mine will draw your life out, hitting your forehead'.