Sunan an-Nasa'i, Volume 5, Book 37, Hadith 3976 (DarusSalam) ⓘ

It was narrated that Abu Hurairah said: "The Messenger of Allah [SAW] said: 'I have been commanded to fight the people until they say La ilaha illallah. If they say it then their blood and their wealth are safe from me, except for a right that is due, and their reckoning will be with Allah.' When the people apostatized, 'Umar said to Abu Bakr: 'Will you fight them when you heard the Messenger of Allah [SAW] say such and such?' He said: 'By Allah, I do not separate Salah and Zakah, and I will fight whoever separates them.' So we fought alongside him, and we realized that that was the right thing."

أَخْبَرَنَا زِيَادُ بْنُ أَيُّوبَ، قَالَ حَدَّثَنَا مُحَمَّدُ بْنُ يَزِيدَ، قَالَ حَدَّثَنَا سُفْيَانُ، عَنِ الزُّهْرِيِّ، عَنْ عُبَيْدِ اللَّهِ بْنِ عَبْدِ اللَّهِ بْنِ عُتْبَةَ، عَنْ أَبِي هُرَيْرَةَ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏ "‏ أُمِرْتُ أَنْ أُقَاتِلَ النَّاسَ حَتَّى يَقُولُوا لاَ إِلَهَ إِلاَّ اللَّهُ فَإِذَا قَالُوهَا فَقَدْ عَصَمُوا مِنِّي دِمَاءَهُمْ وَأَمْوَالَهُمْ إِلاَّ بِحَقِّهَا وَحِسَابُهُمْ عَلَى اللَّهِ ‏" ‏ ‏.‏ فَلَمَّا كَانَتِ الرِّدَّةُ قَالَ عُمَرُ لأَبِي بَكْرٍ أَتُقَاتِلُهُمْ وَقَدْ سَمِعْتَ رَسُولَ اللَّهِ صلى الله عليه وسلم يَقُولُ كَذَا وَكَذَا ‏.‏ فَقَالَ وَاللَّهِ لاَ أُفَرِّقُ بَيْنَ الصَّلاَةِ وَالزَّكَاةِ ‏.‏ وَلأُقَاتِلَنَّ مَنْ فَرَّقَ بَيْنَهُمَا ‏.‏ فَقَاتَلْنَا مَعَهُ فَرَأَيْنَا ذَلِكَ رُشْدًا ‏.‏ قَالَ أَبُو عَبْدِ الرَّحْمَنِ سُفْيَانُ فِي الزُّهْرِيِّ لَيْسَ بِالْقَوِيِّ وَهُوَ سُفْيَانُ بْنُ حُسَيْنٍ ‏.‏