Muhammad, son of Abu Bakr (the First Caliph) was the favourite disciple and companion of Imam Ali (a). Imam Ali (a) had treated and trained him like his own child and had appointed him as the Governor of Egypt. Later on Imam Ali (a) called him back from Egypt and sent Maalik Ashtar as the Governor. Muhammad thought that he was deposed and felt sad about it. When Imam Ali (a) came to know of this he wrote the following letter to him.
I am given to understand that you feel sorry and aggrieved because I called you back and sent Maalik in your place as the Governor of Egypt. The fact of the case is that I did not bring about this change because I found you weak and inefficient and wanted to make you more energetic and strong but because as a change I wanted to send you to a place where the work was easier and which you would find more congenial.
Undoubtedly the man whom I sent as the Governor of Egypt was very faithful to us and very severe against our enemies. May Allah bless him as he finished the days of life assigned to him and left this world. He died in such a state that we were pleased with him. May Allah grant him His highest reward.
You come out of your house, armed with superior intelligence and the best armours, ready to face the enemies. Be ready to fight those who fight against you. Advise the people to obey the orders of the Lord and ask His help as much and as often as you can so that He may grant success to you in your important affairs and may help you in your difficulties.