When the Messenger of Allah ﷺ passed away and Abu Bakr succeeded him, and some of the Arabs reverted to disbelief, Umar said to Abu Bakr, "How can you fight people when the Messenger of Allah ﷺ said, 'I have been commanded to fight people until they declare that there is no god but Allah. Whoever says, There is no god but Allah, has protected his property and his life from me, except for what is due upon them, and their reckoning is with Allah'?"Abu Bakr replied, "By Allah, I will fight whoever separates prayer from zakat, for zakat is the due of wealth. By Allah, if they withhold from me even a young she-camel's tether that they used to give to the Messenger of Allah ﷺ, I will fight them for withholding it."Umar said, "By Allah, it was nothing other than that I saw that Allah had opened Abu Bakr's heart to the fight, and I knew it was the truth."Ibn Bukayr and Abdullah narrated from Layth using the word "anaq" (a young she-goat) instead, and this is more accurate.
حدثنا قتيبة بن سعيد حدثنا ليث عن عقيل عن الزهري أخبرني عبيد الله بن عبد الله بن عتبة
لما توفي رسول الله ﷺ واستخلف أبو بكر بعده وكفر من كفر من العرب قال عمر لأبي بكر كيف تقاتل الناس وقد قال رسول الله ﷺ أمرت أن أقاتل الناس حتى يقولوا لا إله إلا الله فمن قال لا إله إلا الله عصم مني ماله ونفسه إلا بحقه وحسابه على الله فقال والله لأقاتلن من فرق بين الصلاة والزكاة فإن الزكاة حق المال والله لو منعوني عقالا كانوا يؤدونه إلى رسول الله ﷺ لقاتلتهم على منعه فقال عمر فوالله ما هو إلا أن رأيت الله قد شرح صدر أبي بكر للقتال فعرفت أنه الحق قال ابن بكير وعبد الله عن الليث عناقا وهو أصح