Abu Ubaidah ibn al-Jarrah
After that Abu Bakr asked people to appoint as Khalifa either to Umar or Abu Ubaidah ibn al-Jarrah because both of them were Muhajirs from Quraysh, were among the very first who accepted Islam and were among the closest companions of Prophet. But Umar withdrew himself saying that he would never consider himself when Abu Bakr is present. Then Bashir ibn Sa'ad was the first one who pledged at the hand of Abu Bakr, then Umar and Abu Ubaidah ibn al-Jarrah and after that all people at Saqifah followed them.