Is the sale of a bird in flight valid?
Chapter on Selling the Musarrah (Animal with milk retained in udder)
Al-Mughni
Book of Sales
Primary text
The sale of a bird in flight is invalid, whether it is owned or unowned. If owned, it is invalid because it is not capable of being delivered. If unowned, it is invalid for two reasons: the inability to deliver it and the fact that it is not the seller's property. The established principle for this is the Prophet's prohibition against selling *gharar*, which is interpreted to include selling a bird in the air or fish in the water. There is no known disagreement on this matter.
Supporting text
There is no distinction based on whether the bird is accustomed to returning or not, because current delivery is impossible; delivery is only possible upon its return. In response to the argument that a distant absent item also cannot be delivered immediately, the distinction lies in that the absent item can be summoned and brought back, whereas the bird's owner cannot compel its return; it returns only by its own volition, making the owner incapable of guaranteeing its delivery.