Musnad Ahmad 1018:135

Abu Bakr al-Hanafi narrated to us, 'Abd al-Hamid ibn Ja'far narrated to us, from 'Amr ibn Shu'ayb, from the daughter of Kardama, from her father, that he asked the Messenger of Allah, may Allah bless him and grant him peace, and said: "I have vowed to slaughter three of my camels." He said: "If it is at a gathering of the gatherings of Jahiliyyah, or at a festival of the festivals of Jahiliyyah, or for an idol, then do not. But if it is for other than that, then fulfill your vow." He said: "O Messenger of Allah, the mother of this girl has a vow to walk [to the Ka'bah]; should I walk on her behalf?" He said: "Yes."