William Muir,
The Caliphate: Its Rise, Decline and Fall…
“ Abu 'Obeida remonstrated: "Today you have done a scandalous thing in the eyes of the people of the land." 'Omar's feelings were hurt. "O Abu 'Obeida, would that another than you had said that to me! Just think! We were the most obscure and despised of men and the feeblest, and God has glorified us by Islam. If you seek to glorify it in another way, God will humble you." Another account states that it was Abu 'Obeida who appeared in public in a coarse woollen dress, and was reproved: "See, you are commander-in-chief of the armies in Syria, and we are surrounded by enemies. ”
