It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that when the Prophet (peace and blessings be upon him) conquered Khaybar, he stipulated with them that the land and everything yellow and white (that is, gold and silver) would be his. The people of Khaybar said: "We know the land better." So he (peace and blessings be upon him) gave it to them on the condition that they would work it, and half of the produce would be theirs and half would belong to the Muslims. The narrator states that he (peace and blessings be upon him) gave them (the land) on that condition. Then, when the time came to cut the dates, he (peace and blessings be upon him) sent Sayyiduna Ibn Rawahah (may Allah be pleased with him) to them, and he estimated the dates; this is what the people of Madinah call 'khars' (estimation). He stated such-and-such an amount (in the estimate), and they (the people of Khaybar) said: "O Ibn Rawahah, you have been excessive with us." He said: "Then I will take the dates (myself) at this estimate and give you half of the amount I stated." They said: "This is the truth, and by it the heavens and the earth stand. We are content with what you have said."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 14015