Muhammad bin 'Abdullah محمد بن عبد الله بن بزيع · The Book of Jihad

"When Abu Bakr mobilized to fight them, 'Umar said: 'O Abu Bakr, how can you fight the people when the Messenger of Allah (ﷺ) said: "I have been commanded to fight the people until they say La ilaha illallah (there is none worthy or worship except Allah). Whoever says La ilaha illallah, his life and his property are safe from me, except for its right, and his reckoning will be with Allah?'" Abu Bakr, may Allah be pleased with me…