Hadith no. 1847 (below) is a repeat. Read it here.
Volume 3, Book 34, Number 352 :
Narrated by Ibn ‘Umar (radiallaahu `anhu)
Allah’s Apostle (sallallaahu `alayhi wasallam) forbade Najsh.
Volume 3, Book 34, Number 353 :
Narrated by ‘Abdullah bin ‘Umar (radiallaahu `anhu)
Allah’s Apostle (sallallaahu `alayhi wasallam) forbade the sale called ‘Habal-al-Habala which was a kind of sale practiced in the Pre-lslamic Period of ignorance. One would pay the price of a she-camel which was not born yet would be born by the immediate offspring of an extant she-camel.
Habal al-Habalah (حَبَلِ الْحَبَلَةِ): A type of prohibited sale that was prevalent in pre-Islamic Arabia where the fetus of a camel was sold while it was still in the womb of the she-camel. Some fuqaha defined this sale as a spot sale of a camel’s fetus, while others defined it as a deferred sale whereby the price would be paid at the time a she-camel gives birth to the fetus, subject-matter of the contract. In both cases, this sale is forbidden because, according to the first definition, it amounts to the sale of a non-existent, unknown, and non-deliverable object (which is also not owned or possessed by the seller), while, according to the second definition, it is a sale in which the price payment is deferred to an unspecified or unknown date, with deferment being accounted for in the price.