Umar (Arabic Transliteration: `Umar ibn al-Khattāb, c. 586-590 CE – 7 November, 644), also known as Umar the Great or Farooq the Great was the most powerful of the four Rashidun Caliphs and one of the most powerful and influential Muslim rulers.[1] He was a sahabi (companion) of the Islamic prophet Muhammad. He succeeded Caliph Abu Bakr (632–634) as the second Caliph of Rashidun Caliphate on 23 August 634. He was an expert jurist and is best known for his justice with Muslims and non-Muslim subjects alike, that earned him the title Al-Farooq (The one who distinguishes between good and bad) and his house as Darul Adal (house of justice). also, Omar was the first Caliph to be called (Amir al-Mu'minin; Commander of the Faithful).
Under Umar the Islamic empire expanded at an unprecedented rate ruling the whole Sassanid Persian Empire and more than two thirds of the Eastern Roman Empire.[2] His legislative abilities, his firm political and administrative control over a rapidly expanding empire and his brilliantly coordinated multi-prong attacks against Sassanid Persian Empire that resulted in conquest of Persian empire in less then two years, marked his reputation as a great political and military leader.[3] It was Umar who for the first time in 500 years since expulsion of Jews from the Holy Land, allowed them to practice their religion freely and live in Jerusalem.
Religiously a controversial figure in the Muslim world, Umar is regarded by Sunni Muslims as one of four Rashidun or rightly guided caliphs who were true successors of Muhammad; in stark contrast, regarded by Shi'a Muslims as unjust in his usurpation of Ali's right to the caliphate, indeed as the principal political architect of opposition to Ali.