Oaths and Vows (Kitab Al-Aiman Wa Al-Nudhur)
Dawud :: Book 21 : Hadith 3290
Narrated Abdullah ibn Abbas:
A man came to Prophet (peace_be_upon_him) and said: Apostle of Allah, my sister has taken a vow to perform hajj on foot. The Prophet (peace_be_upon_him) said: Allah gets no good from the affliction your sister imposed on herself, so let her perform hajj riding and make atonement for her oath.