Woman's Hair Covering

It seems to me that women observing Jewish religion wear head covering. Has this been part of Israelite tradition since days of antiquity according to Torah or this much later tradition?

Shalom! 

Thank you for your question. 

Yes, the sign of an observant Jewish woman is a woman who covers her hair upon marriage. 

Although the hair covering is not explicitly mentioned in the Torah, we do derive the requirement for a married woman to cover her hair from the Torah, as follows: 

In the book of Number, chapter 5, we read about the “Sotah.” The Sotah was a woman suspected of committing adultery. 

If a husband was to suspect his wife of committing adultery, he would have the rabbis/rabbinic court issue a ban on his wife against being alone with the man she is suspected of committing adultery with. If she is again seen secluding herself with this man, and there are witnesses who saw it, the husband is to summon her to the Holy Temple for a very specialized procedure to determine whether she s guilty or innocent of adultery. 

If she is found to be an adulteress, she would die a gruesome death. If she was innocent, she would receive a number of blessings. 

However, here’s the point: as part of the Sotah ordeal, the Torah says that the Kohen/Priest is to “uncover her head and loosen her hair.” 

From here it is derived that a married woman would always have her hair covered. As the Talmud says (Ketubot 72a) 

For it is written, “and he uncovers the head of the woman...” It is an admonishment to the daughters of Israel that they do not go out bare headed.