As-salamu alaikom,
Here's the story of Umar Ibn Khattab ( May Allah be Pleased with him )
http://everything2.com/e2node/Umar%20ibn%20al-Khattab
One day Umar set forth, sword slung about his neck, with the intention of killing Muhammad(s), having heard that he(s) and some of his Companions had gathered in a particular house. Along the way, he was spotted by Nu'aym Ibn Abdullah, who was already a Muslim. Nu'aym asked him where he was going. Umar informed him of his intention, saying that he would settle the matter once and for all that day. Nu'aym told him that he was letting his anger get the best of himself, and besides, he should put his own house in order. Umar asked what he meant by that, and Nu'aym told him that his own sister, Fatima bint al-Khattab and her husband, who was also his cousin, Sa'id Ibn Zayd had converted to Islam. Hearing this, Umar became enraged and went to his sister's house.
Fatima and Sa'id were listening to Khabbab Ibn Al-Aratt reading Sura Ta-Ha from the Quran at the time. When they heard Umar approach, Khabbab hid himself in a small room and Fatima hid the manuscript beneath her thigh. Umar had already heard them, however, and asked what was it that he had heard. He told them that he had heard that they had become followeres of Muhammad(s) and attacked Sa'id.. Fatima attempted to help her husband, and Umar struck her severely. They both declared that they were, in fact, Muslims and told him to do whatever he will. Umar looked upon his sister, now bleeding from his blow, and his anger gave way to shame. He asked her to show him what they had been reading, as Umar was literate.
Fatima told him that she was afraid of what he might do with it, so he promised that he would not destroy it. She then told him that he was unclean and could not touch it, so he arose and took a bath. He read a few lines and commented on how noble and sublime the speech of the Quran was. Khabbab then came out and said
"O 'Umar, by God, I hope that Allah would bless you with His Prophet's (PBUH) call; for I heard him just last night imploring earnestly; "O Allah, strengthen Islam by Abul Hakam (Abu Jahl) or 'Umar Ibn al-Khattab. Now, 'Umar have some fear of God."
Umar then asked Khattab to lead him to the Messenger of God(s) so that he could accept Islam. Khabbab told him of his(s) location, and Umar took his sword and went there. Umar knocked on the door, and one of the Sahaba looked through a hole in the door to see who it was. He then went to the Prophet(s) and told him that Umar was outside, armed with his sword. Hamza, one of the companions, suggested that he be allowed in, and if his intent was peaceful, then things would be alright, but if intended otherwise, they would kill him with his own sword. The Prophet(s) told them to let him in and went forth to greet him.
What for have you come, O son of Khattab? By God, I see that some calamity is to befall you before you have the final summons.
Umar replied, meekly:
O Messenger of Allah, I have come to attest my faith in Allah and His Prophet (Peace Be Upon Him) and what he has brought from God.
The Messenger of God(s) cried out Allahu Akbar so loudly that everyone in the house knew that Umar had accepted Islam.
