Musannaf Ibn Abi Shayba 7:273

Narrated to us Abd al-Rahim and Abu Khalid al-Ahmar, from Hajjaj, from al-Hakam, from Ali, regarding a man who makes it incumbent upon himself to walk to the House of Allah: Abd al-Rahim said: He may ride and shed blood (sacrifice an animal). And Abu Khalid said: He shall offer a camel (badana) as a sacrificial gift.