Abu Bakr innovated by ordering the murder of Muslims who refused to pay taxes to his government.

Reference: Musnad Ahmad 239

Musnad Ahmad 239
It was narrated that `Ubaidullah bin `Abdullah bin `Utbah said:

When the apostates apostatised at the time of Abu Bakr,1 ‘Umar said: How can you fight the people, O Abu Bakr, when the Messenger of Allah (ﷺ) said: “I have been commanded to fight the people until they say La ilaha illallah (There is no god but Allah),2 and whoever says La ilaha illallah, his wealth and his life are protected from me except in cases dictated by Islamic law, and his reckoning will be with Allah`?3 Abu Bakr said: By Allah, I will most certainly fight those who separate prayer and zakah,4 for zakah is what is due on wealth. By Allah, if they withhold from me a small she-goat that they used to give to the Messenger of Allah (ﷺ), I will certainly fight them for withholding it. `Umar bin al-Khattab said. By Allah, as soon as I saw that Allah had opened Abu Bakr`s heart to the idea of fighting, I knew that he was right.

حَدَّثَنَا عَبْدُ الرَّزَّاقِ، حَدَّثَنَا مَعْمَرٌ، عَنِ الزُّهْرِيِّ، عَنْ عُبَيْدِ اللَّهِ بْنِ عَبْدِ اللَّهِ بْنِ عُتْبَةَ، قَالَ لَمَّا ارْتَدَّ أَهْلُ الرِّدَّةِ فِي زَمَانِ أَبِي بَكْرٍ رَضِيَ اللَّهُ عَنْهُ قَالَ عُمَرُ كَيْفَ تُقَاتِلُ النَّاسَ يَا أَبَا بَكْرٍ وَقَدْ قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ أُمِرْتُ أَنْ أُقَاتِلَ النَّاسَ حَتَّى يَقُولُوا لَا إِلَهَ إِلَّا اللَّهُ فَإِذَا قَالُوا لَا إِلَهَ إِلَّا اللَّهُ عَصَمُوا مِنِّي دِمَاءَهُمْ وَأَمْوَالَهُمْ إِلَّا بِحَقِّهَا وَحِسَابُهُمْ عَلَى اللَّهِ فَقَالَ أَبُو بَكْرٍ رَضِيَ اللَّهُ عَنْهُ وَاللَّهِ لَأُقَاتِلَنَّ مَنْ فَرَّقَ بَيْنَ الصَّلَاةِ وَالزَّكَاةِ فَإِنَّ الزَّكَاةَ حَقُّ الْمَالِ وَاللَّهِ لَوْ مَنَعُونِي عَنَاقًا كَانُوا يُؤَدُّونَهَا إِلَى رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ لَقَاتَلْتُهُمْ عَلَيْهَا قَالَ عُمَرُ رَضِيَ اللَّهُ عَنْهُ فَوَاللَّهِ مَا هُوَ إِلَّا أَنْ رَأَيْتُ أَنَّ اللَّهَ قَدْ شَرَحَ صَدْرَ أَبِي بَكْرٍ رَضِيَ اللَّهُ عَنْهُ لِلْقِتَالِ فَعَرَفْتُ أَنَّهُ الْحَقُّ‏.‏

Grade: Sahih (Darussalam)
Reference  : Musnad Ahmad 239
In-book reference  : Book 2, Hadith 154

Note: 1. This hadith relates specifically to those that were fought during the ridda wars.
2. Umar was astounded that Abu Bakr wanted to fight Muslims - those who recite La ilaha illallah
3. He will be held to account by Allah for failing his religious obligations such as zakat, not the Prophet.
4. The Prophet never went to war over zakat, and hence, Abu Bakr's ridda wars were biddah.

So many companions and hafiz of the Quran were murdered at Yamamah, the Quran was at risk of being lost.
Jami` at-Tirmidhi 3103
Narrated Az-Zuhri:

"From 'Ubaid bin As-Sabbaq, that Zaid bin Thabit narrated to him, he said: 'Abu Bakr As-Siddiq sent for me - (regarding) those killed at Al-Yamamah - and 'Umar bin Al-Khattab was with him. He (Abu Bakr) said: "'Umar came to me and said: The fighting inflicted many casualties among the reciters of the Qur'an on the Day of Al-Yamamah, and I fear that there will be more casualties among the reciters in other parts of the land,1 such that much of the Qur'an may be lost.


In my view, you should order that the Qur'an be collected.'" Abu Bakr said to 'Umar: "How can I do something which was not done my the Messenger of Allah (ﷺ)?" 'Umar said: 'By Allah! It is something good.' 'Umar continued trying to convince me until Allah opened up my chest to that which He had opened the chest of 'Umar, and I saw it as he saw it." Zaid said: 'Abu Bakr said: "You are a young wise man, and we have no suspicions of you. You used to write down the Revelation for the Messenger of Allah as the Qur'an was revealed." He (Zaid) said: 'By Allah! If they had ordered to move one of the mountains it would have been lighter on me than that.' He said: 'I said: "How will you do something which was not done by the Messenger of Allah (ﷺ)?" Abu Bakr said: "By Allah! It is something good." Abu Bakr and 'Umar continued trying to convince me, until Allah opened up my chest for that, just as He had opened their chests, the chest of Abu Bakr and the chest of 'Umar. So I began searching for Qur'anic material from parchments, leaf stalks of date-palms and Al-Likhaf - meaning stones - and the chests of men. I found the end of Surah Bara'ah with Khuzaimah bin Thabit: Verily, there has come to you a Messenger from among yourselves. It grieves him that you should receive any injury or difficulty. He is eager for you; for the believers (he is) full of pity, kind, and merciful. But if they turn away, say: "Allah is sufficient for me. There is no god but He, in Him I put my trust, and He is the Lord of the Mighty Throne (9:128 & 129).'"

حَدَّثَنَا مُحَمَّدُ بْنُ بَشَّارٍ، حَدَّثَنَا عَبْدُ الرَّحْمَنِ بْنُ مَهْدِيٍّ، حَدَّثَنَا إِبْرَاهِيمُ بْنُ سَعْدٍ، عَنِ الزُّهْرِيِّ، عَنْ عُبَيْدِ بْنِ السَّبَّاقِ، أَنَّ زَيْدَ بْنَ ثَابِتٍ، حَدَّثَهُ قَالَ بَعَثَ إِلَىَّ أَبُو بَكْرٍ الصِّدِّيقُ مَقْتَلَ أَهْلِ الْيَمَامَةِ فَإِذَا عُمَرُ بْنُ الْخَطَّابِ عِنْدَهُ فَقَالَ إِنَّ عُمَرَ بْنَ الْخَطَّابِ قَدْ أَتَانِي فَقَالَ إِنَّ الْقَتْلَ قَدِ اسْتَحَرَّ بِقُرَّاءِ الْقُرْآنِ يَوْمَ الْيَمَامَةِ وَإِنِّي لأَخْشَى أَنْ يَسْتَحِرَّ الْقَتْلُ بِالْقُرَّاءِ فِي الْمَوَاطِنِ كُلِّهَا فَيَذْهَبَ قُرْآنٌ كَثِيرٌ وَإِنِّي أَرَى أَنْ تَأْمُرَ بِجَمْعِ الْقُرْآنِ ‏.‏ قَالَ أَبُو بَكْرٍ لِعُمَرَ كَيْفَ أَفْعَلُ شَيْئًا لَمْ يَفْعَلْهُ رَسُولُ اللَّهِ صلى الله عليه وسلم فَقَالَ عُمَرُ هُوَ وَاللَّهِ خَيْرٌ فَلَمْ يَزَلْ يُرَاجِعُنِي فِي ذَلِكَ حَتَّى شَرَحَ اللَّهُ صَدْرِي لِلَّذِي شَرَحَ لَهُ صَدْرَ عُمَرَ وَرَأَيْتُ فِيهِ الَّذِي رَأَى قَالَ زَيْدٌ قَالَ أَبُو بَكْرٍ إِنَّكَ شَابٌّ عَاقِلٌ لاَ نَتَّهِمُكَ قَدْ كُنْتَ تَكْتُبُ لِرَسُولِ اللَّهِ صلى الله عليه وسلم الْوَحْىَ فَتَتَبَّعِ الْقُرْآنَ ‏.‏ قَالَ فَوَاللَّهِ لَوْ كَلَّفُونِي نَقْلَ جَبَلٍ مِنَ الْجِبَالِ مَا كَانَ أَثْقَلَ عَلَىَّ مِنْ ذَلِكَ قَالَ قُلْتُ كَيْفَ تَفْعَلُونَ شَيْئًا لَمْ يَفْعَلْهُ رَسُولُ اللَّهِ صلى الله عليه وسلم فَقَالَ أَبُو بَكْرٍ هُوَ وَاللَّهِ خَيْرٌ ‏.‏ فَلَمْ يَزَلْ يُرَاجِعُنِي فِي ذَلِكَ أَبُو بَكْرٍ وَعُمَرُ حَتَّى شَرَحَ اللَّهُ صَدْرِي لِلَّذِي شَرَحَ صَدْرَهُمَا صَدْرَ أَبِي بَكْرٍ وَعُمَرَ فَتَتَبَّعْتُ الْقُرْآنَ أَجْمَعُهُ مِنَ الرِّقَاعِ وَالْعُسُبِ وَاللِّخَافِ يَعْنِي الْحِجَارَةَ الرِّقَاقَ وَصُدُورِ الرِّجَالِ فَوَجَدْتُ آخِرَ سُورَةِ بَرَاءَةَ مَعَ خُزَيْمَةَ بْنِ ثَابِتٍ ‏:‏ ‏(‏ قَدْ جَاءَكُمْ رَسُولٌ مِنْ أَنْفُسِكُمْ عَزِيزٌ عَلَيْهِ مَا عَنِتُّمْ حَرِيصٌ عَلَيْكُمْ بِالْمُؤْمِنِينَ رَءُوفٌ رَحِيمٌ * فَإِنْ تَوَلَّوْا فَقُلْ حَسْبِيَ اللَّهُ لاَ إِلَهَ إِلاَّ هُوَ عَلَيْهِ تَوَكَّلْتُ وَهُوَ رَبُّ الْعَرْشِ الْعَظِيمِ ‏)‏ ‏.‏ قَالَ أَبُو عِيسَى هَذَا حَدِيثٌ حَسَنٌ صَحِيحٌ ‏.‏

Grade: Sahih (Darussalam)
Reference  : Jami` at-Tirmidhi 3103
In-book reference  : Book 47, Hadith 155
The Prophet said the consequence of wittholding zakat is the witholding of rain - not death by the Muslim army.

Reference: Sunan Ibn Majah 4019

Sunan Ibn Majah 4019
It was narrated that ‘Abdullah bin ‘Umar said:

“The Messenger of Allah (ﷺ) turned to us and said: ‘O Muhajirun, there are five things with which you will be tested, and I seek refuge with Allah lest you live to see them: Immorality never appears among a people to such an extent that they commit it openly, but plagues and diseases that were never known among the predecessors will spread among them. They do not cheat in weights and measures but they will be stricken with famine, severe calamity and the oppression of their rulers. They do not withhold the Zakah of their wealth, but rain will be withheld from the sky, and were it not for the animals, no rain would fall on them. They do not break their covenant with Allah and His Messenger, but Allah will enable their enemies to overpower them and take some of what is in their hands. Unless their leaders rule according to the Book of Allah and seek all good from that which Allah has revealed, Allah will cause them to fight one another.’”

حَدَّثَنَا مَحْمُودُ بْنُ خَالِدٍ الدِّمَشْقِيُّ، حَدَّثَنَا سُلَيْمَانُ بْنُ عَبْدِ الرَّحْمَنِ أَبُو أَيُّوبَ، عَنِ ابْنِ أَبِي مَالِكٍ، عَنْ أَبِيهِ، عَنْ عَطَاءِ بْنِ أَبِي رَبَاحٍ، عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ، قَالَ أَقْبَلَ عَلَيْنَا رَسُولُ اللَّهِ ـ صلى الله عليه وسلم ـ فَقَالَ ‏ "‏ يَا مَعْشَرَ الْمُهَاجِرِينَ خَمْسٌ إِذَا ابْتُلِيتُمْ بِهِنَّ وَأَعُوذُ بِاللَّهِ أَنْ تُدْرِكُوهُنَّ لَمْ تَظْهَرِ الْفَاحِشَةُ فِي قَوْمٍ قَطُّ حَتَّى يُعْلِنُوا بِهَا إِلاَّ فَشَا فِيهِمُ الطَّاعُونُ وَالأَوْجَاعُ الَّتِي لَمْ تَكُنْ مَضَتْ فِي أَسْلاَفِهِمُ الَّذِينَ مَضَوْا ‏.‏ وَلَمْ يَنْقُصُوا الْمِكْيَالَ وَالْمِيزَانَ إِلاَّ أُخِذُوا بِالسِّنِينَ وَشِدَّةِ الْمَؤُنَةِ وَجَوْرِ السُّلْطَانِ عَلَيْهِمْ ‏.‏ وَلَمْ يَمْنَعُوا زَكَاةَ أَمْوَالِهِمْ إِلاَّ مُنِعُوا الْقَطْرَ مِنَ السَّمَاءِ وَلَوْلاَ الْبَهَائِمُ لَمْ يُمْطَرُوا وَلَمْ يَنْقُضُوا عَهْدَ اللَّهِ وَعَهْدَ رَسُولِهِ إِلاَّ سَلَّطَ اللَّهُ عَلَيْهِمْ عَدُوًّا مِنْ غَيْرِهِمْ فَأَخَذُوا بَعْضَ مَا فِي أَيْدِيهِمْ ‏.‏ وَمَا لَمْ تَحْكُمْ أَئِمَّتُهُمْ بِكِتَابِ اللَّهِ وَيَتَخَيَّرُوا مِمَّا أَنْزَلَ اللَّهُ إِلاَّ جَعَلَ اللَّهُ بَأْسَهُمْ بَيْنَهُمْ ‏"‏ ‏.‏

Grade: Sahih (Darussalam)
Reference  : Sunan Ibn Majah 4019
In-book reference  : Book 36, Hadith 94
Abu Bakr: "Kill them by every means, by fire or whatever else... if they deny payment of the alms tax, raid them without any warning."
Tarikh al-Tabari, Vol. 10 Page 100
Narrated Suwayd b. al-Math'abah al-Riyahi:

Khalid b. al-Walid arrived in al-Butah, whereupon he found no one there; he found that Malik had dispersed them among their flocks and forbidden them to gather when he became perplexed over his situation. [In doing so] he said, "Oh Banu Yarbu`, we have disobeyed our commanders, inasmuch as they called us to this religion, whereas the people held us back from it, so that we have neither prospered nor succeeded. I have reconsidered this situation and found it feasible for them without any managing (siyasah). For lo, the situation is one that the people do not manage. Beware of acting in a hostile manner against a group having a mandate [from God to exercise authority]1; so disperse to your territories and enter into this cause." So they dispersed accordingly to their flocks, and Malik went out until he returned to his residence.


When Khalid reached al-Butah, he scattered portions of the army and ordered them to summon [the people] to Islam, and to bring to it whoever had not [yet] responded; and if he resisted, to kill him. [This] was part of that with which Abu Bakr had charged him "When you encamp someplace, make the call to prayer and the iqamah. Then, if the people make the call to prayer and the iqamah, leave them alone; but if they do not do so, there is no [course] but to raid them. [In that case] kill them by every means, by fire or whatever else. And if they respond to you in the call to Islam, then question them [further]; if they affirm [payment of] the alms tax, then accept that from them; but if they deny it, then there is no [course] but to raid them without any word [of warning]."

Book  : Tarikh at-Tabari
Author  : Muhammad ibn Jarir al-Tabari (224 AH - 310 AH)
English reference  : Vol. 10, Page 100
Arabic reference  : 
Narrated by: Abu Ja`far, from al-Sari b. Yahya, from Shu`ayb b. Ibrahim, from Sayf b. `Umar, from Khuzaymah b. Shajarah al-`Uqfani, from `Uthman b. Suwayd, from Suwayd b. al-Math'abah al-Riyahi.

Note: 1. Umar ibn Khattab, when explaining Saqifah, describes the assention to khilfah as "sudden" but Allah (swt) "saved them from its bad consequnces", and hence, nobody would reasonably describe the Khilafah of Abu Bakr a mandate from Allah (swt) to excecise authority. We can hence conclude he is speaking of Ali, who did make such a claim, as is evidenced by the event of the Nomination of Uthman

The Prophet said: Punishment with fire is done by none except Allah.

Reference: Sunan Abi Dawud 2673

Sunan Abi Dawud 2673
Narrated Hamzah al-Aslami:

The Messenger of Allah (ﷺ) appointed him commander over a detachment. He said: I went out along with it. He (the Prophet) said: If you find so-and-so, burn him with the fire. I then turned away, and he called me. So I returned to him, and he said: If you find so-and-so, kill him, and do not burn him, for no one punishes with fire except the Lord of the fire.

حَدَّثَنَا سَعِيدُ بْنُ مَنْصُورٍ، حَدَّثَنَا مُغِيرَةُ بْنُ عَبْدِ الرَّحْمَنِ الْحِزَامِيُّ، عَنْ أَبِي الزِّنَادِ، حَدَّثَنِي مُحَمَّدُ بْنُ حَمْزَةَ الأَسْلَمِيُّ، عَنْ أَبِيهِ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم أَمَّرَهُ عَلَى سَرِيَّةٍ قَالَ فَخَرَجْتُ فِيهَا وَقَالَ ‏"‏ إِنْ وَجَدْتُمْ فُلاَنًا فَاحْرِقُوهُ بِالنَّارِ ‏"‏ ‏.‏ فَوَلَّيْتُ فَنَادَانِي فَرَجَعْتُ إِلَيْهِ فَقَالَ ‏"‏ إِنْ وَجَدْتُمْ فُلاَنًا فَاقْتُلُوهُ وَلاَ تُحْرِقُوهُ فَإِنَّهُ لاَ يُعَذِّبُ بِالنَّارِ إِلاَّ رَبُّ النَّارِ ‏"‏ ‏.‏

Grade: Sahih (Al-Albani)
Reference  : Sunan Abi Dawud 2673
In-book reference  : Book 15, Hadith 197