Then Moses prayed: "My Lord! Indeed I have no control except my brother and myself, so you separate between us and these transgressing people".
It is told in verses 7: 150-151: "When Moses returned to his people, he saw his people worshipping a calf made up of ornaments. By seeing this he became extremely angry. He threw down the Stone disc (Torah) and seized his brother Haroon’s hair. Haroon said: 'Oh son of my mother! The people made me weak and about to kill me, and so you let not give chance for my enemies to rejoice over me, and you don’t count me among the wrongdoing people'. Thus realizing the truth, Moses prayed as: ‘Oh, my Lord! You forgive my brother and me and you admit us unto Your Mercy, You are the Most Merciful of those who show Mercy’". See explanation 2: 99 and 5: 47-49.