Hadith 8:94
He said that God’s Messenger forbade [taking hire for] a stallion's covering. Bukhari transmitted it.
وَعَنْهُ قَالَ: نَهَى رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ عَنْ عَسْبِ الْفَحْلِ. رَوَاهُ الْبُخَارِيُّ
Original Reference: Mishkat al-Masabih 2856