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"And when Moosaa (Moses) returned to his people, angry and grieved, he said: "What an evil thing is that which you have done (i.e, worshipping the calf) during my absence, Did you hasten and go ahead as regards the matter of your Lord (you left His worship)?" And he threw down the Tablets and seized his brother by (the hair of) his head and dragged him towards him, Harun (Aaron) said: "O son of my mother! Indeed the people judged me weak and were about to kill me, so make not the enemies rejoice over me, nor put me amongst the people who are Dhaalimoon (wrong-doers)."" [Al-A'raaf (7):150]

Narrated Al-Ahnaf bin Qais:

While I was going to help this man ('Ali Ibn Abi Talib), Abu Bakra met me and asked, "Where are you going?" I replied, "I am going to help that person." He said, "Go back for I have heard Allah's Apostle saying, 'When two Muslims fight (meet) each other with their swords, both the murderer as well as the murdered will go to the Hell-fire.' I said, 'O Allah's Apostle! It is all right for the murderer but what about the murdered one?' Allah's Apostle replied, "He surely had the intention to kill his companion." [The Book of Faith Volume 1, Book 2, Hadeeth 30]