Musannaf Ibn Abi Shayba 28:963

Waki’ narrated to us, he said: Isra’il narrated to us, from Abu Ishaq, from al-Harith, from Ali, he said: Whoever tethers a horse in the way of Allah, its dung, its urine, and its fodder—and he said such and such—will be in his balance on the Day of Resurrection.