And the moment itself, in the tradition
For the two seconds before the shout, the tradition has something, and it is not what people usually quote. The single most circulated text on anger in Muslim material is graded weak, so it is not used here. What is sound is the following.
The strong one is not the one who overpowers people, it is the one who controls himself when he is angry. A man asked for advice and was told, do not become angry, repeatedly. And kindness does not enter a thing without adorning it. Alongside those, two verses. Had you been harsh and hard hearted they would have scattered from around you. And when two prophets were sent to a tyrant, the instruction was to speak gently.
Qur’an and Sunnah
فَقُولَا لَهُۥ قَوۡلࣰ ا لَّيِّنࣰ ا لَّعَلَّهُۥ يَتَذَكَّرُ أَوۡ يَخۡشَىٰ
Speak to him gently so that he may take heed, or show respect.’
Qur’an 20:44
فَبِمَا رَحۡمَةࣲ مِّنَ ٱللَّهِ لِنتَ لَهُمۡۖ وَلَوۡ كُنتَ فَظًّا غَلِيظَ ٱلۡقَلۡبِ لَٱنفَضُّواْ مِنۡ حَوۡلِكَۖ فَٱعۡفُ عَنۡهُمۡ وَٱسۡتَغۡفِرۡ لَهُمۡ وَشَاوِرۡهُمۡ فِي ٱلۡأَمۡرِۖ فَإِذَا عَزَمۡتَ فَتَوَكَّلۡ عَلَى ٱللَّهِۚ إِنَّ ٱللَّهَ يُحِبُّ ٱلۡمُتَوَكِّلِينَ
By an act of mercy from God, you [Prophet] were gentle in your dealings with them- had you been harsh, or hard-hearted, they would have dispersed and left you- so pardon them and ask forgiveness for them. Consult with them about matters, then, when you have decided on a course of action, put your trust in God: God loves those who put their trust in Him
Qur’an 3:159
Narrated Abu Huraira:Allah's Messenger (ﷺ) said, "The strong is not the one who overcomes the people by his strength, but the strong is the one who controls himself while in anger
Sahih al-Bukhari 6114graded sound, sahihaynfull report
Narrated Abu Huraira:A man said to the Prophet (ﷺ) , "Advise me! "The Prophet (ﷺ) said, "Do not become angry and furious." The man asked (the same) again and again, and the Prophet (ﷺ) said in each case, "Do not become angry and furious
Sahih al-Bukhari 6116graded sound, sahihaynfull report
A'isha, the wife of Allah's Apostle (ﷺ), reported Allah's Apostle (ﷺ) as saying:Kindness is not to be found in anything but that it adds to its beauty and it is not withdrawn from anything but it makes it defective
Sahih Muslim 2594graded sound, sahihaynfull report
Translation: M.A.S. Abdel Haleem, The Qur'an, Oxford University Press, 2004.