Abu Ubaidah ibn al-Jarrah
Umar is reported to have later regretted over his decision of dismissing Khalid from army, accepting the fact that he (Khalid) was not like as he (Umar) thought of him. On his death bed, Umar is also reported to have wished that beside Abu Ubaidah ibn al-Jarrah, if Khalid would be alive he would have appointed him his successor.