It is narrated from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both): In the time of the Messenger of Allah (peace and blessings be upon him), we used to buy grain, so he (peace be upon him) would appoint people over us who would instruct us that we must move the grain from the place where we bought it before selling it elsewhere.
Hadith Referenceالسنن المأثورة / باب في البيوع / 225
Hadith Takhrijصحیح بخاری، البيوع، باب منتهى التلقى، رقم: 2166، صحیح مسلم، البيوع، باب بطلان بيع المبيع قبل القبض، رقم: 1527