Hadith 506170
Chapter 17: Zakat - كتاب الزكاة
وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ عَبْدِ اللَّهِ بْنِ دِينَارٍ، أَنَّهُ قَالَ سَأَلْتُ سَعِيدَ بْنَ الْمُسَيَّبِ عَنْ صَدَقَةِ الْبَرَاذِينِ، فَقَالَ وَهَلْ فِي الْخَيْلِ مِنْ صَدَقَةٍ
Yahya related to me from Malik that Abdullah ibn Dinar said, "I asked Said ibn al-Musayyab about zakat on work-horses, and he said, 'Is there any zakat on horses ?' "
Reference Muwatta Malik 506170
USC-MSA web (English) reference : Book 17, Hadith 41