When Abd al-Rahman bin Muljam wounded Imam Ali (a) who was then offering the morning prayers in the Mosque of Kufa, Imam Ali (a) advised Imam Hasan (a) and Imam Husayn (a) in the following words.
I advise you to fear Allah, do not go after this vicious world though it may try to entice you, do not seek it though it may seek you and do not grieve over and pine for things which this world refuses you. Let the eternal Reward and Blessings of Allah be the prompting factors for all that you say and do. Be an enemy of tyrants and oppressors and be a friend and helper of those who are oppressed and tyrannized.
To you, to my other children, to my relatives and to all who acquire this will of mine, I advise to fear Allah and to be pious, to have fair and honest dealings with one another and improve mutual relations because I have heard your grandfather, the Holy Prophet (s) saying, “To remove mutual enmity, ill-feeling and hatred is better than recommended prayers and fasting”.
Fear Allah when the question of helpless orphans arises. You should never let them starve. So long as you are there to guard and protect them they should not be ruined or lost. The Holy Prophet (s) had always advised, cautioned and reminded us of this responsibility, so much so that we often thought that the Prophet of Allah (s) might on the next occasion assign them a share from our heritage.
Fear Allah in respect of the Holy Qur’an, lest others should excel and surpass you in following its tenets and in acting according to its orders. Fear Allah so far as prayers are concerned because prayers are pillars of your faith. Fear Allah in the matter of His Holy House (Kaa’ba). Let it not be deserted because if it is deserted, you (the Muslims) will be lost.
Do not forget Allah, struggle in His cause with your tongue, with your wealth and with your lives.
Develop mutual liking, friendship and love and help one another. Take care that you do not spurn and treat one another badly and unsympathetically.
Exhort people to do good and abstain them from evil, otherwise the vicious and the wicked will be your overlord and if you willingly allow such persons to be your rulers then your prayers will not be heard by Allah.
O' sons of Abdul Muttalib! Let there be no retaliation for the act of my murder, do not roam about with a drawn sword and with the slogan: “Amir al-Mu'minin is killed”, and do not start the massacre of my opponents and enemies.
See to it that only one man, that is my assassin, is killed, as the punishment of the crime of murder is death and nobody else is molested. The punishment to the man who attempted the murder shall take place only when I die of the wound delivered by him and this punishment shall be only one stroke of sword to end his life. He should not be tortured before his death, his hands and feet should not be amputated because I have heard the Holy Prophet (s) saying: “Do not amputate hands and feet of anybody, be it a biting dog”.