Muwatta Malik, Book 17, Hadith 22 (USC-MSA)

Yahya related to me from Malik from Abdullah ibn Dinar from Abu's-Salih as-Samman that Abu Hurayra used to say, "Anyone who has wealth on which he has not paid zakat will, on the day of rising, find his wealth made to resemble a whiteheaded serpent with a sac of venom in each cheek which will seek him out until it has him in its power, saying, 'I am the wealth that you had hidden away.' "

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ عَبْدِ اللَّهِ بْنِ دِينَارٍ، عَنْ أَبِي صَالِحٍ السَّمَّانِ، عَنْ أَبِي هُرَيْرَةَ، أَنَّهُ كَانَ يَقُولُ مَنْ كَانَ عِنْدَهُ مَالٌ لَمْ يُؤَدِّ زَكَاتَهُ مُثِّلَ لَهُ يَوْمَ الْقِيَامَةِ شُجَاعًا أَقْرَعَ لَهُ زَبِيبَتَانِ يَطْلُبُهُ حَتَّى يُمْكِنَهُ يَقُولُ أَنَا كَنْزُكَ ‏.‏

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also referenced under: Book 17, Hadith 601 (In-Book)