Musnad Abu Ya'la al-Mawsili 154:178

Ali narrated to us, [who said]: Sakhr ibn Juwayriyah informed me, from Nafi’, from Ibn Umar, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "A resident shall not sell for a bedouin." And he said: "Do not meet the caravans for trade, and let none of you sell over the sale of another, and let none of you propose to a woman who has already been proposed to by his brother, until the first suitor leaves it or gives him permission, then he may propose."