Reference for Nedarim 60:6
<big><strong>גמ׳</strong></big> מאי טעמא מדלא קאמר מבעלי שיער
BUT MAY [BENEFIT] FROM WOMEN AND CHILDREN, BECAUSE ONLY MEN ARE CALLED 'BLACK-HAIRED'. What is the reason? — Men sometimes cover their heads and sometimes not; but women's hair is always covered, and children are always bareheaded.<span class="x" onmousemove="('comment',' Hence women would be referred to as 'those of covered hair', and children as 'the bare-headed'. — Ran. In Mishnaic times it was the universal practise for women's hair to be covered, and its violation was deemed sufficient ground for divorce without payment of the kethubah (Keth. 72a Mishnah.) From the present passage it appears that no distinction was drawn between married and unmarried women, but later on custom became more lenient with respect to unmarried women (Shulhan 'Aruk', O.H. 75, 2; cf. Sanh. (Sonc. ed.) p. 398. n. 1, referring to Gentiles). As for men, it was considered a sign of reverence and piety to cover the head (Kid. 31a, Shab. 118b); nevertheless only in the case of great scholars was it held to be indispensable (cf. Kid. 8a. ');"><sup>3</sup></span>