Hats are usually worn in religions as a demonstration of respect to God, as well as to showcase believers' commitment to their faith and cultural identity. Conservative Muslims and Jews often wear head coverings on an everyday basis as a show of respect and modesty, although there is some debate as to whether the requirement is actually mandated by their individual scriptures. While conservative Christians do not don specific religious headgear, among some Christian denominations it is common for women, but not men, to wear hats during church service. The custom is linked to several Bible verses, including 1 Corinthians 11:2-6, which says “every man who prays or prophesies with his head covered dishonors his head, but every wife who prays or prophesies with her head uncovered dishonors her head."

Judaism

The head coverings worn by Jews are based on the denomination of the religion they belong to. While Orthodox Jewish men are mandated to cover their head with a skull cap known as a kippah, Reform and Liberal Jews believe the covering of the head is optional. Meanwhile, Orthodox Jewish women will cover their heads with either a scarf or hat. According to the BBC, Jews believe head coverings are a sign of respect and fear of God, although there is disagreement in the religion as to whether covering one’s head is a Torah commandment.

Islam

In Islam the hijab, or headscarf, is worn by women as an expression of modesty and Muslim identity. But while some in the West may see the wearing of the headscarf–as well as more extensive coverings like the burqa–as religious oppression, the Quran does not actually mandate women to wear those coverings, BBC News reports. The decision to wear one is ultimately a matter of individual choice. The Quran advises both men and women to cover their bodies with modest garments.

Christianity

Although Christian tradition does not mandate everyday head coverings for men or women, there are a variety of head coverings worn among cardinals of the Roman Catholic Church. The most basic is a round skullcap called the zucchetto, according to Slate, while certain occasions call for the biretta, a taller square-ridged hat with three peaks on top. Those are typically worn when entering and leaving a church for Mass. Both of the hats are red, symbolizing how the cardinal should be willing to spill his blood for the church like Jesus Christ.

Other Religions

Various other groups, outside of the world’s three largest faiths, also mandate some kind of head covering. For instance, Sikh men will traditionally wear a turban in public, a practice that was originally advocated by Guru Gobind Singh as a way of protesting the rule of the Hindu aristocracy, SikhNet reports.
Among Zoroastrians, both men and women are required to wear a head covering–usually a pill-boxed shape skull cap–at all times, according to the Zoroastrianism Heritage Institute. Zoroastrianism teaches that the one of the most powerful centers of spiritual knowledge is located on the crown of the head, which must be kept at a constant warm temperature to function properly.