The Messenger of Allah ﷺ dispatched an expedition and placed Usama bin Zayd in command. Some people criticized his appointment, so the Messenger of Allah ﷺ stood up and said, "If you criticize his command now, you also criticized the command of his father before him. By Allah, he was truly worthy of command and was among the dearest of people to me, and this one is among the dearest of people to me after him."
بعث رسول الله ﷺ بعثا، وأمر عليهم أسامة بن زيد، فطعن الناس في إمرته، فقام رسول الله ﷺ فقال: إن تطعنوا في إمرته فقد كنتم تطعنون في إمرة أبيه من قبل، وأيم الله إن كان لخليقا للإمرة، وإن كان لمن أحب الناس إلي، وإن هذا لمن أحب الناس إلي بعده.
Reported by Bukhari in the Book of Rulings (7187), and Muslim in the Book of the Virtues of the Companions (2426:63), through two routes from Abdullah bin Dinar, who heard Ibn Umar say what follows.Sheikh Islam bin Taymiya said, "The combination of strength and trustworthiness is rare among people. This is why Umar bin Khattab used to say, 'O Allah, I complain to You of the boldness of the wicked and the incapacity of the trustworthy.' The duty in every position of authority is to appoint whoever is most suitable for it. So if two men present themselves, one of them of greater trustworthiness and the other of greater strength, the one more beneficial for that particular position and less harmful in it should be given precedence. Thus in command of wars, the strong, courageous man is given precedence, even if he has some corruption in him, over the weak, incapable man, even if he is trustworthy.This is illustrated by the question put to Imam Ahmad about two men who could serve as commanders in a military campaign, one of them strong but corrupt, and the other righteous but weak, asking with which of them the campaign should be undertaken. He said, 'As for the strong but corrupt one, his strength benefits the Muslims while his corruption harms only himself. As for the righteous but weak one, his righteousness benefits only himself while his weakness harms the Muslims. So the campaign should be undertaken with the strong but corrupt one.'The Prophet ﷺ said, "Indeed Allah supports this religion through a corrupt man." And it was also narrated, "through people who have no share in the Hereafter." If the man is not corrupt, he is even more deserving of command in war than someone more righteous than him in religion, provided the more righteous one cannot fill his place.This is why the Prophet ﷺ employed Khalid bin Walid in war from the time he embraced Islam, and said, "Khalid is a sword that Allah has drawn against the polytheists," even though Khalid sometimes did things the Prophet ﷺ disapproved of.The Prophet ﷺ once placed Amr bin As in command, in the expedition of Dhat al-Salasil, in order to win over the goodwill of his relatives to whom he had sent him, even over men who were better than him. And he placed Usama bin Zayd in command for the sake of avenging his father's death.Likewise, the Prophet would employ a man for an outweighing benefit, even though there might be, alongside that commander, someone superior to him in knowledge and faith."Majmu Fatawa (28/254–256).