Hadith 506000
Chapter 17: Zakat - كتاب الزكاة
حَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، عَنْ عَبْدِ اللَّهِ بْنِ دِينَارٍ، أَنَّهُ قَالَ سَمِعْتُ عَبْدَ اللَّهِ بْنَ عُمَرَ، وَهُوَ يُسْأَلُ عَنِ الْكَنْزِ، مَا هُوَ فَقَالَ هُوَ الْمَالُ الَّذِي لاَ تُؤَدَّى مِنْهُ الزَّكَاةُ .
Yahya related to me from Malik that Abdullah ibn Dinar said, "I heard Abdullah ibn Umar being asked what kanz was and he said, 'It is wealth on which zakat has not been paid.' "
Reference Muwatta Malik 506000
USC-MSA web (English) reference : Book 17, Hadith 21