Musannaf Ibn Abi Shaybah 22784 — Going out to meet goods before they

Muhammad (may Allah have mercy on him) said that we have been forbidden to go outside the city and buy goods from caravan people at a low price. If, despite this prohibition, a person goes outside the city and buys, then the owner of the goods will have the option when he arrives in the city. (If he wishes he may cancel the first sale.)