"So Abu Bakr decided to fight them, then 'Umar said: 'O Abu Bakr, how can you fight the people when the Messenger of Allah [SAW] 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 [SAW], 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.'" (Using translation from Nasāʾī 3975)
قَالَ رَسُولُ اللهِ ﷺ أُمِرْتُ أَنْ أُقَاتِلَ النَّاسَ حَتَّى يَقُولُوا لَا إِلَهَ إِلَّا اللهُ فَإِذَا قَالُوهَا عَصَمُوا مِنِّي دِمَاءَهُمْ وَأَمْوَالَهُمْ وَحِسَابُهُمْ عَلَى اللهِ قَالَ فَلَمَّا قَامَ أَبُو بَكْرٍ وَارْتَدَّ مَنْ ارْتَدَّ أَرَادَ أَبُو بَكْرٍ قِتَالَهُمْ قَالَ عُمَرُ كَيْفَ تُقَاتِلُ هَؤُلَاءِ الْقَوْمِ وَهُمْ يُصَلُّونَ؟ قَالَ فَقَالَ أَبُو بَكْرٍ وَاللهِ لَأُقَاتِلَنَّ قَوْمًا ارْتَدُّوا عَنِ الزَّكَاةِ وَاللهِ لَوْ مَنَعُونِي عَنَاقًا مِمَّا فَرَضَ اللهُ وَرَسُولُهُ لَقَاتَلْتُهُمْ قَالَ عُمَرُ فَلَمَّا رَأَيْتُ اللهَ شَرَحَ صَدْرَ أَبِي بَكْرٍ لِقِتَالِهِمْ عَرَفْتُ أَنَّهُ الْحَقُّ