Narrated 'Abdullah: The people used to sell camels on the basis of Habal-al-Habala. The Prophet forbade such sale. Nafi' explained Habalal-Habala by saying. "The camel is to be delivered to the buyer after the she-camel gives birth."
— Sahih Bukhari, Volume 3, Book 35: Sales in which a Price is paid for Goods to be Delivered Later (As-Salam), Hadith #457
