In Name of Allaah, The Most Merciful, The Bestower of Mercy
Amr Ibnul Aas [radiyallaahu-anhu] was one of those given authority and so was Abu Ubaydah Ibn Al-Jarraah [radiyallaahu-anhu]. And Khaalid Ibn Al-Waleed [radiyallaahu-anhu] was given preference over them due to his bravery and usefulness in Jihaad. When Abu Bakr [radiyallaahu-anhu] passed away, Umar Ibnul Khattaab [radiyallaahu-anhu] gave Abu Ubaydah [radiyallaahu-anhu] authority over all of them, because Umar Ibnul khattaab used to be tough for the sake of Allaah, therefore he appointed Abu Ubaydah because he was soft; Abu Bakr was soft and Khaalid was tough. Therefore, the soft one gave authority to the tough one and the tough one gave authority to the soft one to balance the affairs. These two [Abu Bakr and Umar] acted in a manner most beloved to Allaah with regards to fulfilling His Rights.
It has been reported in the Saheeh [i.e. Bukhaari and Muslim] that when the Prophet [sallal-laahu-alayhi-wasallam] consulted his companions regarding the affair of the prisoners of war during the battle of Badr, Abu Bakr [radiyallaahu-anhu] suggested that they should be set free after taking ransom on their behalf and Umar [radiyallaahu-anahu] suggested that they should be executed; so the Prophet [sallal-laahu-alayhi-wasallam] said: Indeed Allaah softens the hearts of men until they become softer than cloth [of linen or cotton], and He toughens the hearts of men until they become tougher than a rock. And your likeness O Abu Bakr is that of Ibraaheem [alayhis-salaam], as Allaah informed us that he said: [فَمَن تَبِعَنِى فَإِنَّهُ ۥ مِنِّىۖ وَمَنۡ عَصَانِى فَإِنَّكَ غَفُورٌ۬ رَّحِيمٌ۬ -But whoever follows me, he verily is of me. And whoever disobeys me, – still You are indeed Oft-Forgiving, Most Merciful]’’ [14:36]; And like Esaa [alayhis-salaam], as Allaah informed us that he said: [إِن تُعَذِّبۡہُمۡ فَإِنَّہُمۡ عِبَادُكَۖ وَإِن تَغۡفِرۡ لَهُمۡ فَإِنَّكَ أَنتَ ٱلۡعَزِيزُ ٱلۡحَكِيمُ – If You punish them, they are Your slaves, and if You forgive them, verily You, only You are the All Mighty, the All Wise].’’ [5:118]
And your likeness O Umar is that of Nuh [alayhis-salaam] as Allaah informed us that he said: [وَقَالَ نُوحٌ۬ رَّبِّ لَا تَذَرۡ عَلَى ٱلۡأَرۡضِ مِنَ ٱلۡكَـٰفِرِينَ دَيَّارًا – And Nuh (Noah) said: ‘My Lord! Leave not one of the disbelievers on the earth!][71:26].
And like Moosaa [alayhis-salaam], as Allaah informed us that he said:
وَقَالَ مُوسَىٰ رَبَّنَآ إِنَّكَ ءَاتَيۡتَ فِرۡعَوۡنَ وَمَلَأَهُ ۥ زِينَةً۬ وَأَمۡوَٲلاً۬ فِى ٱلۡحَيَوٰةِ ٱلدُّنۡيَا رَبَّنَا لِيُضِلُّواْ عَن سَبِيلِكَۖ رَبَّنَاٱطۡمِسۡ عَلَىٰٓ أَمۡوَٲلِهِمۡ وَٱشۡدُدۡ عَلَىٰ قُلُوبِهِمۡ فَلَا يُؤۡمِنُواْ حَتَّىٰ يَرَوُاْ ٱلۡعَذَابَ ٱلۡأَلِيمَ
Our Lord! You have indeed bestowed on Fir’aun (Pharaoh) and his chiefs splendour and wealth in the life of this world, our Lord! That they may lead men astray from Your Path. Our Lord! Destroy their wealth, and harden their hearts, so that they will not believe until they see the painful torment.’’ 10:88
And they (Abu Bakr and Umar) were as the Messenger described them during his lifetime, and they were (also) his vicegerents to the people of the earth.
Source: An excerpt from ‘Adwaa Min Fataawaa Shaikhul Islaam Ibn Taymiyyah (rahimahullaah)’- by Sheikh Saaleh al Fawzaan (may Allaah preserve him)Vol: 2 page 568-569. slightly paraphrased