Musannaf Ibn Abi Shayba 3:5778

'Abd al-Salam ibn Harb narrated to us, from Ibn Abi Farwah, from 'Amr ibn Shu'ayb, from his father, that Mu'adh, 'Uqbah ibn 'Amir, and Ibn Mas'ud said: "Do not let your livestock deceive you. One of you may tread with his livestock upon the humps of the mountains or the bellies of the valleys, and you claim that you are travelers—no, and may there be no honor [in that claim]. Indeed, shortening [the prayer] in travel is [only] for the one who journeys from horizon to horizon."