Jabir bin Abdullah and Abu Sa'id al-Khudri (may Allah be pleased with them both) say that the Messenger of Allah (peace and blessings be upon him) said: "There is no zakah on crops (grain), nor on grapes, nor on dates, except when they reach five wasqs, and that is one hundred faraqs."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الزكاة / 7471