Expedition of Usama bin Zayd The Expedition of Usama bin Zayd also known as the Army of Usama ibn Zaid to al - Balqa , took place in 11AH of the Islamic calendar , in May 632 . Usama ibn Zayd was appointed as the commander of an expeditionary force which was to invade Palestine again ( and attack Moab and Darum ) , on the orders of Muhammad . He set out with 3000 men on the same day Muhammad died , when he reached the destination he attacked the inhabitants , killing many , taking as many captives as he could . Preparation . Muhammad invited Usama to a mosque and ordered him to act as the commander of an army that was to invade Palestine , and attack Takhum of al - Balqa ( which was in Transjordan ) . Usama was the son of Zayd ibn Harithah , a slave that Muhammad freed , and a man that was very close to Muhammad . Zayd ibn Haritha was killed in the Battle of Mutah . In addition to attacking Balqa , he was ordered raid Darum . Some weeks later , Muhammad fell ill , and from his seat ( the Minbar ) in the mosque , he ordered that Usama should lead the expeditionary force . Muhammad also rebuked those that claimed he did not merit such an honour , and rebuked those who claimed he was too young , while the best of Muhammad ’ s commanders were available . He was specifically ordered by Muhammad to go to the place where his father and the Muslim commanders under him , had died and : “ Attack the people of Ubna early in the morning ” . He also ordered him to take women and children captive , instead of killing them . Usama visited Muhammad before he went into battle . The next day he set out for his expedition and learnt Muhammad had died on 8 June 632 . He was told by Abu Bakr to continue the expedition . Invasion of Palestine . 10 Rules of Abu Bakr . According to Tabari , before Usamah headed out , Abu Bakr advised Usamah with " 10 things " , which were like his rules of war . The tradition about the 10 " things " of Abu Bakr are also mentioned in the Sunni Hadith collection Muwatta Imam Malik The tradition mentioned many things , including leaving " monks " alone . Imam Shaffi ( founder of the Shaffi school of thought ) did not consider the tradition , about the 10 rules of Abu Bakr as authentic , but the same book which claimed he did not consider it authentic , also mentioned in another occasion that Shaffi considered it authentic ( or partly authentic ) , and used it to justify killing monks only if they fought Muslims . But the same book explains that even if it was authentic , it does not mean that monks can not be killed , and claims that Abu Bakr ' s intention ( according to Shaffi ) was to only temporarily leave the monasteries alone . Shaffi concluded that " monks " are not included in his list of " non combatants " . It is also worth mentioning that Abu Bakr left Usamah ' s Army against prophet ' s instructions in order to take over control of Muslim lands . Invasion . Usama headed out with 3000 men , of which 1000 were cavalry soldiers . Abu Bakr accompanied Usama part of the way . Usama had also sent a spy , from which he learned that the inhabitants were still unaware of the imminent approach of the army . Usama therefore hurried to Ubna , where he launched a surprise attack with the Muslims shouting their way cry : " Ya Mansur amit " ( “ O ye , Victory , Kill ! ” ) . At the same time , Usama rode his father ’ s horse , and killed the one who slew his father in the Battle of Mutah . Islamic primary sources . Hadith . The incident is mentioned in the Sahih Bukhari hadith collection : It is also mentioned in , , and others . Historical sources . The event is also mentioned by the Muslim scholars Ibn Hisham , Waqidi and Tabari . Tabari said about the event : It is also mentioned by Tabari , that Abu Bakr gave Usamah 10 rules , before he was sent forth and raided the inhabitants : Imam Shaffi ( founder of the Shaffi school of thought ) reportedly did not consider the tradition , about the 10 advice of Abu Bakr as authentic . The 10 advice of Abu Bakr is also mentioned in the Sunni Hadith collection Al - Muwatta . Abu Yusuf mentioned a counter tradition about the instructions of Abu Bakr .