I have been commanded to fight the people until they testify that there is no deity worthy of worship except Allah and that I am the Messenger of Allah. Once they say this, their lives are protected from me, except where the testimony entails a due right; and their reckoning is with Allah.” (1)
Abū Bakr said, “Did he not say, ‘except where it entails a due right; and their reckoning is with Allah’ (2)? Zakat is one such right. By Allah, if they withheld from me even a young she-goat that they used to give to the Messenger of Allah—may Allah bless him and grant him peace—I would fight them for withholding it.”
Umar said, “By Allah, as soon as I saw that Allah had opened Abū Bakr’s heart to fighting, I knew (3) that it was the truth.” (4)
The two Sahih collections confirm Abū Bakr’s understanding in the hadith narrated by Ibn Umar from the Prophet—may Allah bless him and grant him peace—who said:
“I have been commanded to fight the people until they testify that there is no deity worthy of worship except Allah and that I am the Messenger of Allah, establish prayer, and give zakat. Once they do so, their lives and property are protected from me, except where this entails a due right.” (5)
Thus, Umar agreed with Abū Bakr that the apostates who withheld zakat should be fought, as did the rest of the Companions. Those people then accepted the obligation to pay zakat after having refused it (6), and none of their … were taken captive