Musnad Ahmad 33:1165

'Affan narrated to us, Shu'bah narrated to us, Muhammad ibn 'Abd al-Rahman narrated to us, from Muhammad ibn 'Amr ibn Hasan ibn 'Ali, from Jabir ibn 'Abd Allah: That the Messenger of Allah (peace and blessings of Allah be upon him) saw a man who had shade cast over him. He said: "It is not of righteousness to fast while traveling."