عَن أبي هريرةَ أَنَّ رَجُلًا قَالَ لِلنَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسلم: أوصني. قَالَ: «لَا تغضبْ» . فردَّ ذَلِكَ مِرَارًا قَالَ: «لَا تَغْضَبْ» . رَوَاهُ الْبُخَارِيُّ
It is narrated from Abu Hurairah (may Allah be pleased with him) that a man requested the Prophet (peace and blessings of Allah be upon him), "Advise me." The Prophet (peace and blessings of Allah be upon him) said: "Do not get angry." He requested this several times, and the Prophet (peace and blessings of Allah be upon him) (each time) said: "Do not get angry." Narrated by al-Bukhari.