Musannaf Ibn Abi Shayba 13:978

Abu Bakr narrated to us, he said: Ibn ‘Ulayyah narrated to us, from Ibn ‘Awn, from Nafi’, from Ibn ‘Umar, who said: ‘Umar acquired land in Khaybar, so he came to the Prophet, peace and blessings of Allah be upon him, and said: "I have acquired land in Khaybar; I have never acquired property more precious to me than it. So what do you command me to do?" He said: "If you wish, you may withhold its essence and give its produce as charity." He said: So ‘Umar gave it as charity, [stipulating] that its essence shall not be sold, nor given away, nor inherited.