In his letter to the Murtadeen of the Arabian Peninsula during the riddah wars, Abu Bakr threatened to burn them alive if they did not repent from their apostasy. In it he states:
“I have sent you so and so (Khalid Ibn Waleed) with an army of the Muhaajireen, the Ansar, and their good followers and I’ve ordered him not to fight anyone or kill anyone until he calls him to the call of Allaah.
Whoever answers him, accepts the truth, halts his evil and does good, my envoy will accept this from him and will aid him in it. If he refuses, I’ve ordered him to wage war againat them over such, to not spare anyone he is able to kill, to burn them alive with fire, to kill them in a severe manner using all means, to enslave their women and children, and to not accept from any one of them anyhing but Islam.”
[Taareekh At-Tabaree: Al-Bidaayah Wan-Nihaayah]
Note: This was done by the best of all men after the Prophets (as), and it was carried out after the death of the Messenger (saw), so this cancels out the possibility of this being abrogated by the hadeeth. And indeed such an order by Abu Bakr was given to an entire army of Muhaajoreen, Ansar, and Taabi’een, and not a single objected to this order.