Yakub ibn Jau) was a Jewish silk-manufacturer at Cordova, occupying a high position at the court of the Umayyad Caliph Hisham II.
Jacob and his brother Joseph ibn Jau, finding in the court of the palace a large sum of money which had been lost by some Moors from the province during an assault upon them, resolved to use the money for presents for the caliph and the "hajib" al-Mansur ibn Abi Amir, to gain favor thereby.
They accordingly manufactured precious silks for garments, and flags with artistically woven Arabic mottos and emblems, the like of which had never been seen in al-Andalus, and presented them to the caliph and the powerful hajib.
Jacob was also invested with princely splendors; eighteen pages in gold-brocaded garments formed his guard of honor, and a state carriage was always at his disposal.
Jacob deposed Rabbi Hanoch, and called in his place ibn Abitur, who was then staying in the Maghreb.