It was narrated from 'Ikrimah: "Some people apostatized after accepting Islam, and 'Ali burned them with fire. Ibn 'Abbas said: 'If it had been me, I would not have burned them; the Messenger of Allah (ﷺ) said: 'No one should be punished with the punishment of Allah.' If it had been me, I would have killed them; the Messenger of Allah (ﷺ) said: 'Whoever changes his religion, kill him.'"
Source: sunnah.com
Other translations
Arabic
أَخْبَرَنَا مُحَمَّدُ بْنُ عَبْدِ اللَّهِ بْنِ الْمُبَارَكِ، قَالَ حَدَّثَنَا أَبُو هِشَامٍ، قَالَ حَدَّثَنَا وُهَيْبٌ، قَالَ حَدَّثَنَا أَيُّوبُ، عَنْ عِكْرِمَةَ، أَنَّ نَاسًا، ارْتَدُّوا عَنِ الإِسْلاَمِ، فَحَرَّقَهُمْ عَلِيٌّ بِالنَّارِ قَالَ ابْنُ عَبَّاسٍ لَوْ كُنْتُ أَنَا لَمْ، أُحَرِّقْهُمْ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " لاَ تُعَذِّبُوا بِعَذَابِ اللَّهِ أَحَدًا " . وَلَوْ كُنْتُ أَنَا لَقَتَلْتُهُمْ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " مَنْ بَدَّلَ دِينَهُ فَاقْتُلُوهُ " .
sunnah.com