உமர்

'Umar asked 'Ali for the hand of his daughter, Umm Kulthum in marriage. 'Ali replied that she has not yet attained the age (of maturity). 'Umar replied, 'By Allah, this is not true. You do not want her to marry me. If she is underage, send her to me'. Thus 'Ali gave his daughter Umm Kulthum a dress and asked her to go to 'Umar and tell him that her father wants to know what this dress is for. When she came to Umar and gave him the message, he grabbed her hand and forcibly pulled her towards him. 'Umm Kulthum asked him to leave her hand, which Umar did and said, 'You are a very mannered lady with great morals. Go and tell your father that you are very pretty and you are not what he said of you'. With that 'Ali married Umm Kulthum to 'Umar.
=> Tarikh Khamees, Volume 2, p. 384 ('Dhikr Umm Kalthum') and Zakhair Al-Aqba, p. 168.

The marriage of Umm Kulthum to Umar ibn al-Khattab is counted amongst the important issues presented to us by Islamic history, and as one of those matters around which debate and research has continued at length—and still continues. Those who regard this marriage as an authentic fact use it to prove the righteousness of her husband [Umar] and Ali’s acceptance of him. Otherwise, why would he give him his daughter in marriage? As for those who reject the historic occurrence of the marriage, or are of the opinion that it took place under pressure which Umar brought to bear upon Ali use this issue to justify the unrighteousness and viciousness of Umar, and that Ali u did not approve of him
=> A'lam al-Nisaa al-Mu'minat. “A‘lam an-Nisa al-Mu’minat” (p. 182) by Muhammad al-Hassun and Umm ‘Ali Mashkur

Umm Khulthum, who is the daughter of Ameer al-Mu’mineen Ali, Umar proposed to Ali for her hand in marriage during his [Umar’s] caliphate, and at first Ali refused him. So then Umar said what he said, and did what he did.

The original Arabic text is: ام كلثوم هذه هى بنت امير المؤمنين عليه السلام قد خطبها اليه عمر في زمن خلافته فرده اولا فقال عمر ماقال وفعل مافعل
Link
=> Tarikh al-Yaqubi vol. 2 pp.260
 Tarikh al-Madina vol 2 p654
 Tarikh al-Saghir vol. 1 p. 102
 Ma'arif p. 107
 Sunan al-Kubra vol. 4 p. 33
 Siyar Aalam al-Nubalaa 5:22-24
 Tahdhib al-Asmaa wa al-Lughat 2:267 #1219
 al-Hawi lil Fatawa 2:179
 Al-Bidayah wa al-Nihayah vol. 8 p. 14
 Tarikh Dimasqh|Tarikh al Dimashq 42:555
 Al-Mustadrak alaa al-Sahihain, by Hakim al-Nishaburi|al-Hakim al-Nishaburi, 3/142
 al-Istiab fi ma'rifat al-Ashab vol 4 p 509

When Umar asked for the hand of Umm Kulthum, Ali thought to himself: "If I say no, that thing would come to pass which Rasul-Allah tried to prevent, and for which reason he asked me to exercise patience, which is that people will fall into apostacy". "Thus, it was better to hand over Umm Kulthum to him"
al-Istighathah fi Bida' ath-Thalathah, p.90
Shaykh Tabarsi also believed that Umm Kulthum bint Ali married Umar. He wrote the following in his book I‘lam al-Wara bi-A‘lam al-Huda:

As for Umm Kulthoom, she is the one whom Umar ibn al-Khattab married. Our associates say that he (Ali) only married her to him after putting up a lot of resistance, severe refusals and finding excuses. Ultimately he was forced by circumstances to turn her matter over to Abbas ibn ‘Abd al-Muttalib who married her off.
I‘lam al-Wara bi-A‘lam al-Huda - Shaykh Tabarsi.
=>  I'lam al-Wara bi A'lam al-Huda by al-Tabarsi p.204