Sayyiduna Ibn Umar (may Allah be pleased with them both) said: "The Messenger of Allah (peace and blessings be upon him) forbade that the caravans be met on the road (and traded with) before they enter the town, that a town-dweller should sell the goods of a desert-dweller on his behalf, and that any of you should propose marriage over the proposal of his brother, until he either marries or leaves her."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 13223