The 16th of the 42 hadiths gathered by Imam Yahya ibn Sharaf an-Nawawi in An-Nawawi's Forty Hadith, given below in the original Arabic with an English translation and its reference.
عَنْ أَبِي هُرَيْرَةَ رَضِيَ اللهُ عَنْهُ أَنَّ رَجُلًا قَالَ لِلنَّبِيِّ صلى الله عليه و سلم أَوْصِنِي. قَالَ: لَا تَغْضَبْ، فَرَدَّدَ مِرَارًا، قَالَ: لَا تَغْضَبْ" .<br>[رَوَاهُ الْبُخَارِيُّ]
On the authority of Abu Hurayrah (may Allah be pleased with him): A man said to the Prophet (peace and blessings of Allah be upon him), “Counsel me,” so he (peace and blessings of Allah be upon him) said, “Do not become angry.” The man repeated [his request for counsel] several times, and [each time] he (peace and blessings of Allah be upon him) said, “Do not become angry.” [Al-Bukhari]
Text from the open hadith-api dataset. Hadith numbering follows that edition and can differ slightly from a printed copy — check the Arabic against a trusted mushaf of hadith before relying on a reference.