Musnad Ahmad 1127:2

Yazid ibn Harun narrated to us, Muhammad ibn Ishaq informed us, from Ya'qub ibn 'Abdullah ibn al-Ashajj, from Abu Umamah ibn Sahl ibn Hunayf, from Sa'id ibn Sa'd ibn 'Ubadah, who said: There was among our houses a small, weak, sickly, and underdeveloped man. The tribe was suddenly shocked to find him with one of their slave women, committing fornication with her. Sa'd ibn 'Ubadah mentioned that to the Messenger of Allah, peace and blessings of Allah be upon him, and that man was a Muslim. The Messenger of Allah, peace and blessings of Allah be upon him, said: "Strike him with his prescribed punishment." They said: "O Messenger of Allah, he is weaker than that; if we were to strike him a hundred times, we would kill him." He said: "Take a bundle of a hundred thin palm stalks, then strike him with it a single strike." He said: So they did that.