Zaid bin Aslam (may Allah have mercy on him) says that I heard from a man named Shahr, who was a trader. He asked Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) about auction sales (bidding). He (may Allah be pleased with them both) replied: "The Messenger of Allah (peace and blessings be upon him) forbade a man from making a deal over another's deal until he leaves it. Spoils of war and inheritances are exceptions to this."