Sahih Muslim 2143
Sahih Muslim · Book 38: The Book of Manners and Etiquette · The Prohibition Of The Names Malik Al-Amlak Or Malik Al-Muluk "King Of Kings"
Abu Huraira reported from Allah's Messenger (ﷺ) so many ahadith and one of them was this that Allah's Messenger (ﷺ) said:
حَدَّثَنَا مُحَمَّدُ بْنُ رَافِعٍ ، حَدَّثَنَا عَبْدُ الرَّزَّاقِ ، أَخْبَرَنَا مَعْمَرٌ ، عَنْ هَمَّامِ بْنِ مُنَبِّهٍ ، قَالَ هَذَا مَا حَدَّثَنَا أَبُو هُرَيْرَةَ ، عَنْ رَسُولِ اللَّهِ صلى الله عليه وسلم فَذَكَرَ أَحَادِيثَ مِنْهَا وَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " أَغْيَظُ رَجُلٍ عَلَى اللَّهِ يَوْمَ الْقِيَامَةِ وَأَخْبَثُهُ وَأَغْيَظُهُ عَلَيْهِ رَجُلٌ كَانَ يُسَمَّى مَلِكَ الأَمْلاَكِ لاَ مَلِكَ إِلاَّ اللَّهُ " .
The most wretched person in the sight of Allah on the Day of Resurrection and the worst person and target of His wrath would of the person who is called Malik al-Amlak (the King of Kings) for there is no king but Allah.