It is narrated from Sayyiduna Sa'b bin Jaththamah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) was asked about horses trampling the children of the polytheists at night (what is the ruling on this)? He (peace and blessings be upon him) said: "They are of their fathers."
Hadith Referenceالمعجم الكبير للطبراني / باب الصاد / 7417