What is the authenticity of Umar ibn al-Khattab's—may Allah be pleased with him—prohibiting the Muslim nation from wearing the hijab, and what is the refutation against those who use this as evidence that the hijab is not obligatory?

The issue of hijab (definition) is definitively settled by conclusive divine texts. The statement that a woman revealing her charms does not cause temptation is incorrect; rather, it is obstinacy. What Umar, may Allah be pleased with him, did was specific to slave women because they were in a working profession, and it has been authentically reported by Al-Bayhaqi that the head, neck, and what appears of a slave woman during her work are not considered awrah (private parts), unless there is fear of temptation, in which case she must cover herself. There is no contradiction between Umar's action and the clear verses, as the verses apply to free women, while Umar's actions pertain to slave women. Scholars have differed on defining the awrah of a slave woman in relation to a non-mahram (definition) man. Hijab was enjoined by Allah the Almighty, and a Muslim must comply with Allah's command, as Allah the Almighty said: ﴿And it is not for a believing man or a believing woman, when Allah and His Messenger have decided a matter, that they should have [any] option in their decision. And whoever disobeys Allah and His Messenger has certainly strayed into a clear error.﴾ [Al-Ahzab: 36].