Sayyiduna Abdullah bin Umar (may Allah be pleased with them) narrates that the Prophet Muhammad (peace be upon him) said: "Whoever buys a date-palm tree after it has been pollinated, and does not stipulate (at the time of transaction) a condition regarding its fruit, then he will get nothing of it. And whoever buys a slave and does not stipulate a condition regarding the wealth he possesses, then he will get nothing of it."