Ibn Shihab al-Zuhri (may Allah have mercy on him) says: The Prophet (peace and blessings be upon him) had no labourers to work the date palms and crops of Khaybar, so the Prophet (peace and blessings be upon him) called the Jews of Khaybar and handed Khaybar over to them on the condition that they would work it in return for half the produce and would pay (the other half) to the Messenger of Allah (peace and blessings be upon him) and his Companions. The Prophet (peace and blessings be upon him) said to them: "I will let you remain in it for as long as Allah lets you remain." So the Messenger of Allah (peace and blessings be upon him) used to send Sayyiduna Abdullah bin Rawahah (may Allah be pleased with him) to them, and he would estimate the dates when the fruit first began to ripen, before any of it was eaten. Then he would give the Jews the choice either to take the produce at that estimate or to hand it over to them at that estimate.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 14024