Musnad Abu Ya'la al-Mawsili 110:122

Abu al-Rabi' narrated to us, Hafs bin Abi Dawud narrated to us, from Muhammad bin Abd al-Rahman bin Abi Layla, from 'Ata' bin Abi Rabah, from Ibn Abbas, who said: The Messenger of Allah (peace be upon him) was cupped while he was fasting and in the state of Ihram, and he fainted. So, he forbade the people on that day from cupping while fasting, out of dislike for the weakness it would cause them.