1 Corinthians 11:4
ESV - 4 Every man who prays or prophesies with his head covered dishonors his head.
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I am a Messianic Jew. As a former observer of Judaism, I am used to wearing my Kippah throughout a church service. However, prior Christmas I went to a christian church and was corrected using this very verse. Now when I visit this church, I try and observe their christian customs the same way he did in mine.