Muhammad bin Yahya bin Hiban محمد بن يحيى بن حبان · The Book of Jihad

"When the Messenger of Allah (ﷺ) died, some of the 'Arabs apostatized. 'Umar said: 'O Abu Bakr, how can you fight the 'Arabs? Abu Bakr said: 'The Messenger of Allah (ﷺ) said: I have been commanded to fight the people until they testify that La ilaha illallah (there is none worthy of worship except Allah) and that I am the Messenger of Allah, and establish prayer and pay Zakah?' By Allah, if they withhold from me a small she-goat that…

"Allah laughs at two men, one of whom killed the other but they both entered Paradise. The first one fought in the cause of Allah and was killed, then Allah accepted the repentance of the one who killed him, and he fought and was martyred."

"Are you weeping when the Messenger of Allah (ﷺ) is sitting here?" He said: "Let them weep so long as he is among them, but if he dies no one should weep for him."