The Book of Transactions (Kitab Al-Buyu`)
Muslim :: Book 10 : Hadith 3760
Abdullah b. Umar (Allah be pleased with them) reported that Allah's Messenger (may peace be upon him) contracted with the people of Khaibar (land and trees on the condition that they should give) half of the yield from land and trees. The rest of the hadith is the same. In the hadith transmitted on the authority of AIi b. Mushir there is no mention of it, but that A'isha and Hafsa were those who opted for land and water, but he (the narrator) said: He (Hadrat 'Umar, gave option to the wives of Allah's Apostle (may peace be upon him) that land would be earmarked for them, but he made no mention of water.