Sarah was the only woman of Ibrahim's people to believe in Allah. She afterwards became his wife. She stood by her husband all the time when calling his people to Allah. When Ibrahim realized that no other than his wife and his nephew, Lut, was going to believe in his call, he decided to immigrate to a city caller Ur and another called Haran and then departed for Palestine with them. After Palestine, Ibrahim (peace be upon him) arrived in Egypt.
Abu Hurairah narrated that Ibrahim did not tell a lie except on three occasions: twice for the sake of Allah (Exalted and Almighty) when he said: "I am sick," when his people were holding a festival in honor of their gods, Ibrahim excused himself by saying he was sick, (Ch 37:89 Quran) and when he said: "(I have not done this but) the big idol has done it." The third was while Ibrahim and Sarah were on a journey. They passed through the territory of a tyrant. Someone said to the tyrant: "This man Ibrahim is accompanied by a very charming lady." So, he sent for Ibrahim and asked him about Sarah saying "Who is this lady?" Ibrahim said: "She is my sister." Ibrahim went to Sarah and said "O Sarah! There are no believers on the surface of the earth except you and me. This man asked me about you and I have told him that you are my sister. Do not contradict my statement." The tyrant then called Sarah, and when she went to him, he tried to take a hold of her with his hand, with evil intentions, but his hand got stiff and he was confounded. He asked Sarah: "Pray to Allah for me and I shall not harm you." So Sarah asked Allah to cure him and he was cured. He tried to take hold of her for the second time, but his hand got as stiff as or stiffer than before and he was more comfounded. He again requested Sarah: "Pray to Allah for me, and I will not harm you." Sarah asked Allah to again, and he became all right. He then called one of his guards who had brought her and said: "You have not brought me a human being but have brought me a devil." The tyrant then gave Hajar as a maid servant to Sarah. Ibrahim, gesturing with his hand, asked: "What has happened?" Sarah replied: "Allah has spoiled the evil plot of the infidel or immoral person and gave me Hajar for service."
Sarah had not born any children. Ibrahim had aged and his hair was gray after many years spent in calling people to Allah. Sarah thought she and Ibrahim were lonely because she could not have a child. Therefore, she offered her husband her servant Hajar in marriage. Hajar gave birth to her first son Ishmael (Isma'il) when Ibrahim was an old man.
Time passed. One day Ibrahim was sitting outside his tent, three angels descended to the earth. They came in human shapes and saluted Ibrahim. Ibrahim arose and welcomed them. He took them inside his tent thinking they were strangers and guests. He invited his guests to eat and placed before them a sumptuous meal of roasted calf. They were angels and did not eat. The angels gave Sarah glad tidings of the birth of a son, Isaac (Ishaq). She could hardly believe the news. As a "barren old woman" the news seemed to her too good to be true. Allah Almighty says:
There came Our messengers to Abraham with glad tidings. They said, "Peace!" He answered, "Peace!" and hastened to entertain them with a roasted calf. But when he saw their hands went not towards the (meal), he felt some mistrust of them, and conceived a fear of them. They said: "Fear not: We have been sent against the people of Lut." And his wife was standing (there), and she laughed (either, because the Messengers did not eat their food or for being glad for the destruction of the people of Lut). But we gave her glad tidings of Isaac, and after him, of Jacob. She said: "Alas for me! shall I bear a child, seeing I am an old woman, and my husband here is an old man? That would indeed be a wonderful thing!" They said: "Dost thou wonder at Allah's decree? The grace of Allah and His blessings on you, O ye people of the house! for He is indeed worthy of all praise, full of all glory!" (Hud 11: 69-73)
And thus were Sarah and Ibrahim blessed with the miraculous birth of a son in their old age.