Sahih Muslim Book 10, Hadith Number 3759.
Chapter : If the buyer becomes insolvent and the seller finds the commodity sold to the buyer intact. he can take it back.
Ibn Umar (Allah be pleased with them) reported: Allah’s Messenger (may peace be upon him) handed over the land of Khaibar (on the condition) of the share of produce of fruits and harvest, and he also gave to his wives every year one hundred wasqs: eighty wasqs of dates and twenty wasqs of barley. When ‘Umar became the caliph he distributed the (lands and trees) of Khaibar, and gave option to the wives of Allah’s Apostle (may peace be upon him) to earmark for themselves the land and water or stick to the wasqs (that they got) every year. They differed in this matter. Some of them opted for land and water, and some of them opted for wasqs every year. ‘Aisha and Hafsa were among those who opted for land and water.