Messenger of Allah ﷺ sent us in a mission (i.e., an army-unit) and said, "If you find so-and-so and so-and-so, burn both of them with fire." When we intended to depart, Messenger of Allah ﷺ said, "I have ordered you to burn so-and-so and so-and-so, and it is none but Allah Who punishes with fire, so, if you find them, kill them (i.e., don't burn them)."  

أَنَّهُ قَالَ بَعَثَنَا رَسُولُ اللَّهِ ﷺ فِي بَعْثٍ فَقَالَ إِنْ وَجَدْتُمْ فُلاَنًا وَفُلاَنًا فَأَحْرِقُوهُمَا بِالنَّارِ ثُمَّ قَالَ رَسُولُ اللَّهِ ﷺ حِينَ أَرَدْنَا الْخُرُوجَ إِنِّي أَمَرْتُكُمْ أَنْ تُحْرِقُوا فُلاَنًا وَفُلاَنًا وَإِنَّ النَّارَ لاَ يُعَذِّبُ بِهَا إِلاَّ اللَّهُ فَإِنْ وَجَدْتُمُوهُمَا فَاقْتُلُوهُمَا  

ʿAli burnt some people and this news reached Ibn ʿAbbas, who said, "Had I been in his place I would not have burnt them, as the Prophet ﷺ said, 'Don't punish (anybody) with Allah's Punishment.' No doubt, I would have killed them, for the Prophet ﷺ said, 'If somebody (a Muslim) discards his religion, kill him.' "  

لأَنَّ النَّبِيَّ ﷺ قَالَ لاَ تُعَذِّبُوا بِعَذَابِ اللَّهِ وَلَقَتَلْتُهُمْ كَمَا قَالَ النَّبِيُّ ﷺ مَنْ بَدَّلَ دِينَهُ فَاقْتُلُوهُ