Omar ibn al-Khattab is quoted as having said;
"Fatima clutched her hands on the door trying to stop me from opening it. I sought to open it, but I found the challenge too great, so I hit both her hands with the whip, and it caused her pain... I kicked the door, and she had stuck her belly on the door to fortify it... I forced the door open and entered. She faced me with a look which caused my vision to go into a trance, so I slapped her on her cheeks from outside her face’s veil, breaking her earring which scattered on the floor. Ali came out. When I felt his presence, I rushed to get out of the house and said to Khalid (ibn al-Walid) and to Qunfath and those in their company, “I surely have been spared a momentous event.” I gathered a large number of men not to subdue Ali but to make my heart more daring. I went to him, and he was besieged at his house, and took him out of his house..., etc"
Ibid., Vol. 30, pp. 293-95.
Also refer to Sunni historian Abul Hasan, Ali Ibn al-Husain al-Mas'udi who in his book 'Isbaat al-Wasiyyah' describes the events in detail and reports that: "They surrounded Ali and burned the door of his house and pulled him out against his will and pressed Fatimah between the door and the wall killing Mohsin (the male-child she was carrying in her womb for six months).
When the assailants reached her house, `Omer called out, “O Fatima daughter of the Messenger of Allah! Get those who have sought shelter at your house out so that they may swear the oath of allegiance and join the other Muslims who have already done so; otherwise, I, by Allah, shall set them all to fire.
Al-Jamal, pp. 117-18 (new edition). Nahj al-Haqq, p. 271. Al-Imama wal Siyasa, Vol. 1, p. 12. Ibn Shuhnah, Tarikh (referred to in a footnote in Al-Kamil), Vol. 7, p. 164. Abul-Fida’, Tarikh, Vol. 1, p. 156. Al-`Iqd al-Farad, Vol. 4, p. 259. Al-Ya`qabi, Tarikh, Vol. 2, p. 126.
She has said, “They brought the fire to burn the house and our own selves, so I stood at the door’s latch and pleaded to them in the Name of Allah..., etc.”
Al-Majlisi, Bihar al-Anwar, Vol. 30, p. 348, citing Irshad al-Qulab by al-Daylami.
In another text, he is quoted as having said, “O daughter of the Messenger of Allah! By Allah! Nobody is dearer to me than your father and your own self! By Allah! This does not stop me from setting the door of those who have assembled at your house ablaze!”
Muntakhab Kanz al-`Ummal (referred to in a footnote in Ahmed’s Musnad), Vol. 2, p. 174, from Ibn Aba Shaybah. Ibn Abul-Hadid, Sharh Nahjul Balagha, Vol. 2, p. 45 from al-Jawhari and al-Mughni to the judge `Abdullah, Part 20, Section 1, p. 335. Al-Murtada, Al-Shafi, Vol. 4, p. 110.
Also, refer to
http://www.al-islam.org/encyclopedia/chapter4/5.html.
The Eminent Sheikh At-Tusi wrote: “One of the denied facts is that they (Umar and his followers) hit Fatima (the blessing of Allah be upon her) although it has been narrated that they flogged her with a strip and a famous opinion that no one amongst the Shia scholars dispute about, is that Umar hit her on her stomach (womb) until she was forced to have a miscarriage, where the miscarried baby was named Mohassan. The narration (of the event) is even famous amongst them (the Sunnis), as well as the narration of their intention to burn her house when a group of sincere companions who had refused to pay allegiance and sought refuge to her house. And no one can deny this narration because we have proven it from amongst the Sunni sources through the narration of Al-Balathari and others, and the Shia narrations are numerous and our scholars indisputably accept them.”
(Talkhis Al-Shafi 3:156)
The attack on her house occurs
f. Abu Ubayd Al-Qasim bin Salaam (who died in the year 224 A.H) has narrated on the authority of Abdul Rahman bin ‘Ouf that Abu Bakr bin Abi Quhafa said: I wish that I did not raid the house of Fatima and that I left it even if the door was closed to (plan) war. (Al-Amwaal 144)
g. Abul-Qasim Sulayman bin Ahmad At-Tabrani (who died in the year 360 A.H), the author of the book Al-Mu’jam Al-Kabir, has narrated from Abi Bakr ibn Abi Quhafa: As for the three things that I wish I never did, was that I wish I did not raid Fatima’s house and I left it …. (Al-Mu’jam Alkabir 1:62)
h. Ibn Abd-Rabbih Al-Undulosi has narrated in his book, Al-‘Iqdul Farid, from Abdul Rahman bin ‘Ouf that Abi Bakr ibn Abi Quhafa said: And I wish that I did not raid the house of Fatima for any reason even if they had the door closed to (plan) war. (Al-‘Iqdul Farid 4:93)
i. Ibrahim bin Sayyar al-Nazzam; the Mu’tazali (who died in the year 231 A.H) narrated: On the day of pledging allegiance (to Abu Bakr) Umar hit the stomach of Fatima until she miscarried Muhassan. (Al-Wafi bil Wafiyyat 6:17)
j. Muhammad bin Yazid bin Abdil Akbar Al-Baghdadi (who died in the year 285 A.H), the famous author of the book Al-Kamil, narrated from Abdil Rahman bin ‘Ouf from Abi Bakr bin Abi Qohafa: I wish I did not raid Fatima’s house and that I left it even if the door was closed to (plan) war. (Sharh Nahjul Balagha li-ibn Abi Al-Hadid 2:46)
k. Al-Masudi (who died in the year 325 A.H) has narrated in his book titled Muruj Al-thahab: Abu Bakr said at the time of his death: “I wish I did not seek to raid the house of Fatima”, and he mentioned many things about that incident.” (Muruj Al-Thahab 2:301)
l. Ibn Abi Darim (who died in the year 357 A.H) has narrated in his book Mizan Al-I’tidal: Umar kicked Fatima until she miscarried Muhassan. (Mizan Al-I’tidal 3:459)
m. The contemporary historian, Abdul Fattah Abdul Maqsood, stated in his book ‘Imam Ali’: That Umar bin Al-Khattab said “I swear by the One whom Umar’s soul is in His power, they must come out of the house or else I will burn it on whoever is inside it …!”
A group of the people (who were with Umar) who feared Allah and guarded (the teachings of) the Prophet said: “O Aba-Hafs, Fatima is inside!”
He carelessly screamed: “So what … !” He then approached and knocked on the door, then he hit the door open and invaded it … and Ali appeared to him … at that moment Fatima’s voice was heard from the doorway of the house … she was crying for help … (Abdul Fattah Abdul Maqsood: Ali bin Abi Taleb 4:276)
n. Moqatil ibn ‘Atiyyah narrated in his book ‘Al-Imamah wal Khilafah’: After Abu Bakr took the allegiance of people by force, using his sword and power, he sent Umar and Qunfuth and a group of men to the house of Ali and Fatima. Umar collected wood and put them at the doorway of Fatima’s house and burnt the door down … (Al-Imamah wal khilafah 160-161)