After Muhammed, saws, declared that he was a prophet, more and more people became Muslims and many of them were from his own tribe, the Quraysh. Umar was a young man at this time and believed in the traditions of his ancestors. He saw that his tribe the Quraysh were becoming devided by this new religion and he thought and thought what to do, for he was a man of action who thought that it was his duty to do something. He saw that the trouble had one cause only. Remove the man who was that removed, and everything would soon be as it had been before. When a sudden wave of anger took ahold of him, he set out with his sword to go to the house of the Prophet to kill him. As soon as he left his house he came upon a relative of his, Nu’aym. who had become a muslim but had kept it a secret for fear of Umar. Nu’aym saw that Umar was very angry so he asked him where he was going. “I am going to Muhammed, that renegade, who has split Quraysh into two, and I shall kill him.” Nu’aym tried to talk him out of it, but Umar would not listen. So Nu’aym thought of another argument to try. He said, “Oh, Umar, why not first go back to the people of your own house and set them to rights.?” “Who is that?” asked Umar angrily. “Your sister and brother in law” said Nu’aym.
So Umar turned and went directly to his sister, Fatimah's house. It so happened that his sister and brother in law and another man were reciting parts of the Surah Ta Ha as he approached the house, and Umar heard them. He called out angrily to his sister. When they heard the voice of Umar his sister hid the manuscript that they were reading from in the folds of her dress. When Umar came in he said, “What was that jibbering I heard?” They tried to put him off but he then said, “And I hear that you have become followers of Muhammed.” Then he attacked his brother in law and when he sister Fatimah went to the defense of her husband, Umar strick her a blow which broke the skin. “It is true” they said, “We are Muslims and we believe in God and His Messenger. So do what you want to us.” Fatimah’s wound was bleeding and when Umar saw the blood he was sorry for what he had done. A change came over him, and he said to has sister: “Give me that script that I heard you reading, that I may see what it is that Muhammed has brought.” His sister was afraid to give it to him, but he took off his sword and even took ablution when his sister told him he had to in order to touch holy scripture.
Umar began to read and said: "Oh how beautiful and noble are these words!” And by the time he had finished he was in awe of what he had read. He then asked, “Where is Muhammed now that I may see him?” His sister could see that he had softened and said that the Prophet had only the day before prayed that Islam be strengthened by the coming if either Abu Hakam or Umar. He was told that he would find Muhammed with some of his companions near the Safa gate. So he took up his sword and rushed off to find him. Meanwhile, Nu’aym had gone to warn the Prophet that Umar was coming to kill him. So the companions were not surprised when Umar came to the door. But the Prophet was not afraid and said to let him in. Advancing to meet him , he seized him by the belt and pulled him into the middle of the room, saying: “What has brought you here?” Umar answered, “Oh, messenger of Allah, I have come to you that I may declare my faith in God and in His Messenger and in what he has brought from God.” Every one in the house was so glad that Umar had entered Islam.
There was no question of Umar’s keeping his Islam a secret. He wished to tell everyone, especially those who were the most hostile to Islam. Umar became the second most important companion of the Prophet and used his sword in many battles against the enemies of Islam.