Musnad Ahmad 30:2829

'Abd al-Rahman ibn Mahdi narrated to us, from Shu'bah, from al-'Ala' ibn 'Abd al-Rahman, from his father, from Abu Hurayrah, and from Suhayl ibn Abi Salih, from his father, from Abu Hurayrah: "That the Prophet, peace and blessings of Allah be upon him, forbade that a man should bid against the bid of his brother, or propose to a woman to whom his brother has proposed."