Musannaf Ibn Abi Shayba 5:715

Ibn ‘Uyaynah narrated to us, from Ibn ‘Ajlan, from Sa’id ibn Abi Sa’id, that ‘Umar asked a man about some land of his that he had sold. He said to him, "Secure your wealth and bury it beneath your wife’s bed." He said, "O Commander of the Faithful, is it not a treasure (kanz)?" He replied, "It is not a treasure if its Zakat has been paid."