oomis, see this post for source references regarding the Biblical requirement for a married woman to cover hair:
snippet:
“According to Torah law, married women must cover their hair whenever they are outside their home. A woman who fails to do so forfeits her kesubah and should technically be divorced by her husband (Kesuvos 72a; E.H. 115:1-4). Mishnah Berurah 75:14 and Beiur Halachah say it must even be covered inside the home.”