(1) باب
It was narrated that An-Nu'man bin Bashir said:
"We were with the Messenger of Allah [SAW] and a man came and whispered to him. He said: 'Kill him.' Then he said: 'Does he bear witness to La ilaha illallah (there is none worthy of worship except Allah)?' He said: 'Yes, but he is only saying it to protect himself.' The Messenger of Allah [SAW] said: 'Do not kill him, for I have been commanded to fight the people until they say La ilaha illallah, and if they say it, their blood and their wealth are safe from me, except for a right that is due, and their reckoning will be with Allah.'"
Reference: Sunan an-Nasa'i 3979
In-book reference: Book 37, Hadith 14
English translation: Vol. 5, Book 37, Hadith 3984