Abu Huraira said that when Abu Bakr was made the Prophet's successor after his death and infidelity arose among certain Arabs, ‘Umar b. al-Khattab asked Abu Bakr how he could fight with the people when Allah's Messenger ﷺ had said, “I have been commanded to fight with the people till they say there is no Allah but Allah, so whoever says so has protected his property and his person from me except for what is due from him, and his reckoning is left to Allah.” Abu Bakr replied, “I swear by Allah that I will certainly fight with those who make a distinction between prayer and zakat, for the zakat is what is due from property. I swear by Allah that if they were to refuse me a female kid which they used to pay to Allah's Messenger ﷺ I would fight with them over the refusal of it." ‘Umar then said, “I swear by Allah that I clearly saw Allah had made Abu Bakr feel justified in fighting, and I recognised that it was right." (Bukhari and Muslim).