The Holiness Code of the Torah appears to completely forbid the shaving of the corners of the head; as with many other parts of the Holiness Code, the Book of Ezekiel describes similar regulations, stating that the priests should not shave their heads, or let their locks grow long. However, there were clearly exceptions, with the Book of Ezekiel itself adding that priests should keep their hair trimmed, and the Priestly Code of the Torah arguing that, in certain cases of tzaraath, the hair should be completely shaved away. The Priestly Code additionally requires that Nazarites shave their heads, 7 days after any contact with corpses, and the Deuteronomic Code compels captive women to shave their head after the conclusion of mourning for their parents
According to biblical scholars, the shaving of hair was originally a mourning custom, which, according to the Book of Jeremiah, was also practiced by Arabic tribes (although some ancient manuscripts of the text read live in remote places rather than clip the corners of their hair). Biblical scholars think that the regulations against shaving hair may be an attack on the practice of offering hair to the dead, which was performed in the belief that it would obtain protection in sheol; Nazarites shaved after contact with a corpse, captive women shaved after mourning the death of their parents, and the general prohibition in the Holiness Code is immediately followed by a rule against people cutting their own bodies for the benefit of the dead.
Textual scholars date the Priestly Source, and the Holiness and Priestly Codes within it, to the late 7th century or later; it appears that before this time, the shaving of the head during mourning was permitted, and even encouraged. The Book of Amos, which is dated by textual scholars to the mid 7th century, as well as the Books of Isaiah and of Micah, which textual scholars date to a slightly later period, portray Jehovah as instructing the Israelites to shave their head as an act of mourning:
The forbidding of shaving the corners of the head was interpreted by the Mishnah as prohibiting the hair at the temples being cut so that the hairline was a straight line from behind the ears to the forehead; the corners - payot - were defined as the hair from around and above the ears, to the same level as the nose. The Mishnah interpreted the regulation to only apply to males; in response to the Mishnaic definition and the biblical proscription, many Jewish men allowed their hair to grow, and hang down in curls or ringlets.
However, because the biblical prohibition against shaving uses the Hebrew word gelech (גלח), which refers to shaving with a blade against the skin, Talmudic rabbis interpreted it to only refer to single-bladed razors, and only to situations that involve the hair being cut close to the roots, in a smooth manner; thus Maimonides argued that scissors could be used to cut off the sidelocks. Nevertheless, conservative views, such as those of the Shulchan Aruch, argued that cutting the sidelocks was a heathen practice, and therefore they shouldn't be cut by any mechanism.
The Hasidic and Yemenite Jews let their sidelocks grow particularly long. In the wider Haredi community, quite a few men grow sidelocks, but sometimes shorten them or tuck them behind the ears. Among those who grow them long, they are often curled.
The Lithuanian Jews were less influenced by Kabbalistic practises, but still retain sidelocks to a degree, in a small number of variant styles: