It is narrated from Sayyiduna Arib al-Mulayki (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Goodness and nobility are tied to the forelocks of horses until the Day of Resurrection, and their owners are helped in (keeping) them. The one who spends on them is like one who stretches out both his hands in charity, and their urine and dung will be turned, for their owners, into the musk of Paradise with Allah on the Day of Resurrection."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 14577