Musannaf Ibn Abi Shayba 28:507

'Abd al-Rahman ibn Muhammad al-Muharibi narrated to us, from Hajjaj ibn Dinar, from Ibn Sirin, from 'Ubaydah: That Abu Bakr granted a land concession (iqta') to al-Aqra' ibn Habis and 'Uyaynah ibn Hisn, and he wrote a document regarding it.