Sayyiduna Abu Humayd al-Sa'idi (may Allah be pleased with him) says: We set out with the Messenger of Allah (peace and blessings be upon him) on the expedition of Tabuk, and we came in Wadi al-Qura to a garden belonging to a woman. The Messenger of Allah (peace and blessings be upon him) said: "Estimate its yield." So we estimated it, and the Messenger of Allah (peace and blessings be upon him) also estimated it at ten wasqs of dates, and said: "Keep count of it until we return, if Allah wills." Then we went on until we reached Tabuk. Then he narrated the hadith and said: Then we came back until we reached Wadi al-Qura, and the Messenger of Allah (peace and blessings be upon him) asked the woman about the fruit of her garden: "How much did its fruit come to?" She said: It came to ten wasqs.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الزكاة / 7436