Mishkat al-Masabih 19 Jihad كتاب الجهاد 93

وَعَنْ أَبِي وَهَبٍ الْجُشَمِيِّ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: ” ارْتَبِطُوا الْخَيْلَ وامسحُوا بنواصيها وأعجازِها أَو قَالَ: كفالِها وَقَلِّدُوهَا وَلَا تُقَلِّدُوهَا الْأَوْتَارَ ” . رَوَاهُ أَبُو دَاوُدَ وَالنَّسَائِيّ

Aba Wahb al-Jushami reported God’s Messenger as saying, “Tie the horses, rub down their forelocks and rumps (or he said, their buttocks), and put things on their necks, but do not put bowstrings.”* * The reason for this is that bowstrings may injure them. Abu Dawud and Nasa’i transmitted it.