Abdullah bin Dinar (may Allah have mercy on him) said: I heard Abdullah bin Umar (may Allah be pleased with them both) when he was asked about "al-kanz" (hoarded treasure), and he said: It is the wealth whose zakah is not paid.
This is the correct version, mawquf (the Companion's own words).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الزكاة / 7232