Musannaf Ibn Abi Shaybah 38960 — The age of maturity: Abu Hanifah said

Sa'id bin al-Musayyib relates that the Prophet (peace and blessings be upon him) ordered Sayyiduna Attab bin Asid (may Allah be pleased with him) to estimate grapes just as date-palms are estimated. So the zakah of grapes is to be paid in the form of raisins, and the zakah of date-palm fruit in the form of dried dates. This is the Sunnah of the Prophet (peace and blessings be upon him) regarding dates and grapes.