1 Corinthians 11 contains a list of instructions regarding how men and women should present themselves in regards to head coverings and hair length. 1 Corinthians 11:14-15 says
14Doth not even nature itself teach you, that, if a man have long hair, it is a shame unto him?
15But if a woman have long hair, it is a glory to her: for her hair is given her for a covering.
Some more conservative Christians interpret this as applying to all Christian men, while most Christians view it as being wrong in the culture of that particular place and time.