When the Messenger of Allah ﷺ passed away and Abu Bakr was appointed as his successor, some of the Arabs reverted to disbelief. Umar said to Abu Bakr, "How can you fight these people when the Messenger of Allah ﷺ said, 'I have been commanded to fight the people until they say there is no god but Allah. Whoever says there is no god but Allah has protected his wealth and life from me, except by its right, and his reckoning is with Allah'?"Abu Bakr replied, "By Allah, I will fight whoever distinguishes between prayer and zakat, for zakat is the obligation due on wealth. By Allah, if they withhold from me even 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, it was nothing other than that I saw Allah had opened Abu Bakr's heart to the decision to fight, and I knew it was the truth."
أخبرنا قتيبة بن سعيد قال حدثنا الليث عن عقيل عن الزهري أخبرني عبيد الله بن عبد الله بن عتبة
لما توفي رسول الله ﷺ واستخلف أبو بكر 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 قال أبو بكر والله لأقاتلن من فرق بين الصلاة والزكاة فإن الزكاة حق المال والله لو منعوني عقالا كانوا يؤدونه إلى رسول الله ﷺ لقاتلتهم على منعه قال عمر فوالله ما هو إلا أني رأيت الله شرح صدر أبي بكر للقتال فعرفت أنه الحق