Sahih Bukhari | Volume 5 | Hadith Number 183

Narrated by Ibn 'Umar
In the Pre-Islamic period of ignorance the people used to bargain with the meat of camels on the principle of Habal-al-Habala which meant the sale of a she-camel that would be born by a she-camel that had not yet been born. The Prophet forbade them such a transaction.