Musannaf Ibn Abi Shayba 9:1730

Abu Bakr narrated to us, he said: Ibn Mushir and Abu Usamah narrated to us, from Ubaydullah ibn Umar, from Nafi’, from Ibn Umar, he said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "A man should not propose to a woman whom his brother has already proposed to, and he should not sell over the sale of his brother, unless he gives him permission."