Dismissal of Khalid from command
On 22 August 634, Abu Bakr died, having made Umar, Khalid's cousin, his successor. Umar's first move was to relieve Khalid from supreme command of Muslim Forces and appointing Abu Ubaidah as the new commander in chief of the Islamic army.
 Khalid had become a trial of disbelief(fitna) to the Muslims as they had attributed the wins of battles to the personality and figure of Khalid; Umar was reported as saying:"I did not fire khalid ibn al waleed because I am angry with him or because of betrayal of trust or responsibility but the reason was that he was becoming a "fitna" to the people and I wanted people to know that it is Allah who gives victory", this resulted in the dismissal of Khalid from supreme command and later in 638, from military services.
Khalid, gave a pledge of loyalty to the new caliph and continued service as an ordinary commander under Abu Ubaidah.Though Khalid was a part of it. He is reported to have said: "If Abu Bakr is dead and Umar is Caliph, then we hear and obey"