Musnad Ahmad 283:4

Muhammad ibn Ja‘far narrated to us, he said: Shu‘bah narrated to us, he said: Khubayb ibn ‘Abd al-Rahman narrated to us, from ‘Abd al-Rahman ibn Mas‘ud ibn Niyar, from Sahl ibn Abi Hathmah, he said: He came to us while we were in our mosque, and he said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "When you estimate (the yield of dates), take and leave; leave a third. If you do not leave—or find—(Shu‘bah is the one who doubted) a third or a quarter."