Al-Salt bin Zubayd al-Madini relates from his father, from his grandfather, that the Messenger of Allah (peace and blessings be upon him) appointed him to estimate (the produce) and said to him: "Record half for us and leave half for them, for they suffer theft and it does not (all) reach them."
Muhammad said: I narrated this hadith to Ubaydullah bin Umar, and he said: It is established with us that the Prophet (peace and blessings be upon him) said: "Record two thirds for us and leave a third for them."
This chain is majhul (contains unknown narrators); and something on this has been narrated from Umar bin al-Khattab (may Allah be pleased with him).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الزكاة / 7444