Sayyiduna Abu Hurairah (may Allah be pleased with him) narrated that when the Messenger of Allah (peace and blessings of Allah be upon him) passed away and Sayyiduna Abu Bakr (may Allah be pleased with him) became the Caliph, some tribes among the Arabs turned disbelievers (and some refused to pay Zakat, and Sayyiduna Abu Bakr intended to fight them). So Sayyiduna Umar (may Allah be pleased with him) said, "How can you fight with people in the presence of the statement of the Messenger of Allah (peace and blessings of Allah be upon him): 'I have been commanded to fight the people until they testify that there is no god but Allah, and whoever testifies to this, his wealth and life will be safe from me except for its due right (i.e., in cases of retribution, etc.), and his reckoning is with Allah.'" Upon this, Sayyiduna Abu Bakr (may Allah be pleased with him) replied, "By Allah, I will fight everyone who differentiates between prayer and Zakat (i.e., performs prayer but refuses to pay Zakat), for Zakat is the due right of wealth. By Allah, if they withhold even a young she-goat which they used to give to the Messenger of Allah (peace and blessings of Allah be upon him), I will fight them for it." Sayyiduna Umar (may Allah be pleased with him) said, "By Allah, it was nothing but that Allah had opened Abu Bakr's chest for the truth, and later I also realized that Abu Bakr was indeed upon the truth."