Anas ibn Malik reported: Umar left his house holding his sword and he met a man from the tribe of Zahra. He said, “Where are you going?” Umar said, “I intend to kill Muhammad.”

He said, “How will you be secure from the tribe of Hashim and the tribe of Zahra if you killed Muhammad?” Umar said, “It should be done to an apostate.” He said, “What if I told you something amazing? Your brother-in-law and your sister have become apostates and have abandoned your religion.” So Umar came to them while they were both with Khabbab and he heard the recitation. He entered the house and he said, “What was this sound?” And they had been reading Surah TaHa. They both said, “It was nothing.” Umar said, “Perhaps you two have become apostates?” His brother-in-law said, “O Umar, what if the truth is in other than your religion?” So Umar started beating him severely and his sister came to defend to him and Umar struck her on face, making her bleed. She was angry and she said, “The truth is in other than your religion; I testify that there is no God but Allah and Muhammad is His servant and His messenger.” Umar said, “Bring me the book which you were reciting.” His sister said, “Indeed, you are impure and it should only be touched by those who are clean.” So Umar washed and cleaned himself. Then, he took the book and he read Surah TaHa until the verse,

Verily, I am Allah. There is no God but Me, so worship Me and establish prayer for My remembrance.” (20:14)

Umar said, “Take me to Muhammad.” When Khabbab heard what Umar said, he said to him, “Rejoice, O Umar, for I hope the supplication of the Messenger of Allah, peace and blessings be upon him, which he made five nights ago will be answered: O Allah, strengthen Islam with Umar ibn Al-Khattab or Amr ibn Hisham.” At the time, the Messenger of Allah was in a house among other companions, and Umar approached the house until he saw Hamza, Talha, and some other people at the door. Hamza said, “Here is Umar; if Allah intends for him goodness he will embrace Islam, but if Allah intends other than that then we will kill him easily.” The Prophet was inside receiving revelation and he came out to meet Umar. He grabbed him by his shirt and held his sword and he said, “What do you want, O Umar, or will Allah reveal disgrace for you as He revealed it upon Waleed ibn Al-Mughirah? So here is Umar, O Allah, strengthen Islam with Umar.” So Umar said, “I testify that there is no God but Allah and you are the servant of Allah and His messenger.”