Musannaf Ibn Abi Shayba 37:167

Abu Mu'awiyah narrated to us, from al-A'mash, from Abdullah ibn Murrah, from Hudhayfah, who said: If a man were to tether a horse in the way of Allah, and it gave birth to a foal at the time of the first of the signs [of the Hour], he would not ride the foal until he saw the last of them.