It was narrated that Abu Hurairah said:

"So Abu Bakr decided to fight them, then 'Umar said: 'O Abu Bakr, how can you fight the people when the Messenger of Allah ﷺ said: "I have been commanded to fight the people until they say La ilaha illallah, and if they say it, their blood and their wealth will be safe from me except for a right that is due.?' Abu Bakr said: 'I will fight whoever separates prayer and Zakah. By Allah, if they withhold from me a young goat that they used to give to the Messenger of Allah ﷺ, I will fight them for withholding it.' 'Umar said: 'By Allah, as soon as I realized that Allah has expanded the chest of Abu Bakr to fight them, I knew that it was the truth.'"

أَخْبَرَنَا أَحْمَدُ بْنُ سُلَيْمَانَ، قَالَ حَدَّثَنَا مُؤَمَّلُ بْنُ الْفَضْلِ، قَالَ حَدَّثَنَا الْوَلِيدُ، قَالَ حَدَّثَنِي شُعَيْبُ بْنُ أَبِي حَمْزَةَ، وَسُفْيَانُ بْنُ عُيَيْنَةَ، وَذَكَرَ، آخَرَ عَنِ الزُّهْرِيِّ، عَنْ سَعِيدِ بْنِ الْمُسَيَّبِ، عَنْ أَبِي هُرَيْرَةَ، قَالَ فَأَجْمَعَ أَبُو بَكْرٍ لِقِتَالِهِمْ فَقَالَ عُمَرُ يَا أَبَا بَكْرٍ كَيْفَ تُقَاتِلُ النَّاسَ وَقَدْ قَالَ رَسُولُ اللَّهِ ﷺ " أُمِرْتُ أَنْ أُقَاتِلَ النَّاسَ حَتَّى يَقُولُوا لاَ إِلَهَ إِلاَّ اللَّهُ فَإِذَا قَالُوهَا عَصَمُوا مِنِّي دِمَاءَهُمْ وَأَمْوَالَهُمْ إِلاَّ بِحَقِّهَا " . قَالَ أَبُو بَكْرٍ لأُقَاتِلَنَّ مَنْ فَرَّقَ بَيْنَ الصَّلاَةِ وَالزَّكَاةِ وَاللَّهِ لَوْ مَنَعُونِي عَنَاقًا كَانُوا يُؤَدُّونَهَا إِلَى رَسُولِ اللَّهِ ﷺ لَقَاتَلْتُهُمْ عَلَى مَنْعِهَا . قَالَ عُمَرُ فَوَاللَّهِ مَا هُوَ إِلاَّ أَنْ رَأَيْتُ اللَّهَ قَدْ شَرَحَ صَدْرَ أَبِي بَكْرٍ لِقِتَالِهِمْ فَعَرَفْتُ أَنَّهُ الْحَقُّ .