A binding arrangement made in advance
He set it up so that his own anger could not harm anyone.
اللَّهُمَّ إِنِّي اتَّخَذْتُ عِنْدَكَ عَهْدًا لَنْ تُخْلِفَنِيهِ فَأَيُّمَا مُؤْمِنٍ سَبَبْتُهُ أَوْ جَلَدْتُهُ فَاجْعَلْ ذَلِكَ كَفَّارَةً لَهُ يَوْمَ الْقِيَامَةِ
Allāhumma innī-ttakhadhtu ʿindaka ʿahdan lan tukhlifanīh…fa-ayyumā mu'minin ādhaytuhu fa-jʿal dhālika lahu qurbatan ilayka.
“O Allah, I have taken a covenant with You that You will not break: any believer I have harmed, make that a means of nearness to You for him.”
The full narration
Abu Huraira reported Allah's Messenger (ﷺ) as saying:I have held covenant with Thee which Thou wouldst not break, so for any believer whom I curse or beat, make that an expiation on the Day of Resurrection
Source
Ṣaḥīḥ Muslim · 6624
Ṣaḥīḥ
- Agreed upon as authentic (al-Bukhārī / Muslim)