About this time, another very important event took place. Umar(ra), who later became the Second Khalifa of Islam, was still one of the fiercest and the most feared enemies of Islam. He felt that no effective step had yet been taken against the new Movement and decided to put an end to the Prophet's(sa) life. He took his sword and set out. A friend was puzzled to see him going and asked where he was going and with what intent. "To kill Muhammad(sa)," said Umar(ra).
"But would you be safe from his tribe after this? And do you really know how things are going? Do you know that your sister and her husband have joined Islam?"
It came like a bolt from the blue and greatly upset Umar(ra). He decided to go and have done with his sister and her husband first. As he reached their house he heard a recitation going on inside. The voice was that of Khabbab(ra) who was teaching them the Holy Book. Umar(ra) entered the house swiftly. Khabbab(ra), alarmed by the hurried steps, had already hid himself. Umar's(ra) sister, Fatima(ra), put away the leaves of the Qur’an. Confronting her and her husband, Umar(ra) said, "I hear you have renounced your own faith," and, saying this, he raised his hand to strike her husband, who was incidentally his own cousin. Fatima(ra) threw herself between Umar(ra) and her husband; so Umar's(ra) hand fell on Fatima’s(ra) face and struck her on the nose, from which blood flowed freely. The blow made Fatima(ra) all the braver. She said, "Yes, we are Muslims now and shall remain so; do what you may." Umar(ra) was a brave man, though rough. His sister's face, dyed red by his own hand, filled him with remorse. Soon he was a changed man. He asked to be shown those leaves of the Qur’an they were reading from. Fatima(ra) refused lest he should tear them up and throw them away. Umar(ra) promised not to do so. But, said Fatima(ra), he was not clean. Umar(ra) offered to have a bath. Clean and cooled, he took the leaves of the Qur’an in his hand. They contained a portion of the Chapter Ta Ha. And he came upon the verses:
"Verily I am Allah; there is no God beside Me. So serve Me, and observe prayer for My remembrance. Surely the Hour is coming, and I am going to manifest it, that every soul may be recompensed for its endeavour" (20:15, 16).
The firm assertion of God's existence, the clear promise that Islam would soon establish genuine worship in place of the customary one current in Mecca—these and a host of other associated ideas must have moved Umar(ra). He could contain himself no longer. Faith welled up in his heart and he said, "How wonderful, how inspiring!" Khabbab(ra) came out of his hiding, and said, "God is my witness, only yesterday I heard the Prophet(sa) pray for the conversion of Umar(ra) or Amr ibn Hisham. Your change is the result of that prayer." Umar's(ra) mind was made up. He asked where the Prophet(sa) was and made straight for him at Dari Arqam, his bare sword still in his hand. As he knocked at the door, the Prophet's(sa) Companions could see Umar(ra) through the crevices. They feared lest he should have some evil design. But the Prophet(sa) said, "Let him come in." Umar(ra) entered, sword in hand. "What brings you?" inquired the Prophet(sa). "Prophet(sa) of God," said Umar(ra), "I am here to become a Muslim." Allahu Akbar, cried the Prophet(sa). Allahu Akbar, cried the Companions. The hills around Mecca echoed the cries. News of the conversion spread like wild fire and henceforward Umar(ra), the much-feared persecutor of Islam, himself began to be persecuted along with other Muslims. But Umar(ra) had changed. He delighted now in suffering as he had delighted before in inflicting suffering. He went about Mecca, a much harassed person.