Mishkat al-Masabih 6 Zakat كتاب الزكاة 42

عَنْ عَلِيٍّ أَنَّ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ: «لَيْسَ فِي الْخَضْرَاوَاتِ صَدَقَةٌ وَلَا فِي الْعَرَايَا صَدَقَةٌ وَلَا فِي أَقَلَّ مِنْ خَمْسَةِ أَوْسُقٍ صَدَقَةٌ وَلَا فِي الْعَوَامِلِ صَدَقَةٌ وَلَا فِي الْجَبْهَةِ صَدَقَةٌ» . قَالَ الصَّقْرُ: الْجَبْهَةُ الْخَيل وَالْبِغَال وَالْعَبِيد. رَوَاهُ الدَّارَقُطْنِيّ

‘Ali reported the Prophet as saying, “There is no sadaqa on green herbs, palm-trees given in usufruct for a year, less than five camel-loads, working animals, or al-jabha.” As-Saqr said al-jabha* consists of horses, mules and slaves. Daraqutni transmitted it. * Applied usually to horses, meaning the best type.