Musannaf Ibn Abi Shayba 7:274

Ya'la ibn 'Ubayd narrated to us, from al-Ajalih, from 'Amr ibn Sa'id al-Bajali, who said: I was beneath the pulpit of Ibn al-Zubayr while he was upon it. A man came and said: "O Commander of the Faithful, I vowed to perform Hajj walking. When it was such and such time, I walked, but I feared that the Hajj would pass me by, so I rode." He said: "There is no fault upon you. Return next year, and walk the distance you rode, and ride the distance you walked."