Musannaf Ibn Abi Shayba 28:959

Shababa narrated to us, from Abd al-Hamid ibn Bahram, from Shahr ibn Hawshab, from Asma bint Yazid, she said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Indeed, goodness is tied to the forelocks of horses until the Day of Resurrection."