The conversion of 'Umar ibn al Khattab

Perhaps you are familiar with the story of how 'Umar ibn al Khattab became a believer. When he heard the Blessed Prophet was making many converts around Mecca, 'Umar became angry and volunteered, in a meeting of idol-worshippers, to kill Muhammad.
He then stormed through the streets with his sword drawn and vowed to murder him. (At that time, the idol-wordhippers of Mecca were determined to crush Islam.)

On his way, a man who knew him saw the angry look on 'Umar's face and asked him where he was going. When 'Umar replied that he was going to kill Muhammad, the man told him, "Perhaps you should take care of your own house first. Your sister and brother in law already accepted Islam."

When 'Umar heard this he became even angrier and ran off in the direction of his sister's house. When he got there, he heard someone reading something, and he pushed in the door violently. He saw his sister and her husband and another Muslim sitting and reading aloud off a paper.
"Did you became a Muslim!" He yalled.
When his sister, Fatimah bint al Khattab, said they did, he became enraged and started hitting Fatimah's husband. She tried to stop him from punching her husband and grabbed 'Umar.
'Umar swung around and hit his sister in the face. She fell to the ground in tears. She looked up at him and cried, "Do whatever you want to us! We are determined to die as Muslims!"
'Umar paused when he saw the blood on his sister's cheek. He felt terrible inside. He calmed down and stood silently, ashamed at what he had just done. After a minute he asked to see the pages she had been reading from. She told him to wash up with water first. When he finished bathing, he returned and was given the papers.
- On them were written verses from Surah TA HA. (20)
When he reached verse 14 he cried out, "Surely this is the Word of Allah! Take me to Muhammad right now!"
The other Muslim who was there, Khabbab, stood up and declared, "Umar! Good news for you. It seems the prayer of the Holy Prophet which he said last night has been answered in your favor. He had prayed to Allah, 'O Allah, strengthen Islam with either 'Umar ibn al Khattab or 'Umar ibn Hisham. Whomever You please." (12:108)
When 'Umar was brought to the Blessed Prophet, he asked him, " 'Umar, why have you come?"
'Umar replied, "I am here to accept Islam!" When the other Muslims there heard these worlds the shouted for joy and calls of, Allahu Akbar," "Allah is the Greatest!" rang through the streets. The idol-worshippers were stunned. All it took was a few verses from Holy Qur'an to change his heart - those pages and the will and guidance of Allah.