Musnad Ahmad 482:1

Hashim narrated to us, Yahya ibn Sa'id informed me, from 'Ubayd Allah ibn Zahr, from Abu Sa'id, from 'Abd Allah ibn Malik: That the sister of 'Uqbah ibn 'Amir vowed to perform Hajj on foot. 'Uqbah asked the Prophet, peace and blessings of Allah be upon him, about that, and he said: "Command her to ride." He thought that he had not understood him, so when those who were with him had left, he returned and asked him again. He said: "Command her to ride, for Allah, the Mighty and Majestic, is in no need of your sister torturing herself."