It is narrated from Abdul Malik bin Umair (may Allah have mercy on him) that when Hazrat Umar Farooq (may Allah be pleased with him) dismissed Hazrat Khalid bin Waleed (may Allah be pleased with him) in Syria and appointed Hazrat Abu Ubaidah bin Al-Jarrah (may Allah be pleased with him), Hazrat Khalid (may Allah be pleased with him) said: Hazrat Umar (may Allah be pleased with him) has appointed the trustee of this Ummah over you. I heard the Prophet (peace and blessings of Allah be upon him) say: The trustee of this Ummah is Abu Ubaidah bin Al-Jarrah.