That 'Ali burnt some people who apostasized from Islam. This news reached Ibn 'Abbas, so he said: "If it were me I would have killed them according to the statement of Messenger of Allah ﷺ. The Messenger of Allah ﷺ said: 'Whoever changes his religion then kill him.' And I would not have burned them because the Messenger of Allah ﷺ said: 'Do not punish with the punishment of Allah.' So this reached 'Ali, and he said: "Ibn 'Abbas has told the truth."  

لَوْ كُنْتُ أَنَا لَقَتَلْتُهُمْ لِقَوْلِ رَسُولِ اللَّهِ ﷺ مَنْ بَدَّلَ دِينَهُ فَاقْتُلُوهُ وَلَمْ أَكُنْ لأُحَرِّقَهُمْ لِقَوْلِ رَسُولِ اللَّهِ ﷺ لاَ تُعَذِّبُوا بِعَذَابِ اللَّهِ فَبَلَغَ ذَلِكَ عَلِيًّا فَقَالَ صَدَقَ ابْنُ عَبَّاسٍ