Plutarch, Theseus
Bernadotte Perrin, Ed.

5.

Since it was still a custom at that time for youth who were coming of age to go to Delphi and sacrifice some of their hair to the god, Theseus went to Delphi for this purpose, and they say there is a place there which still to this day is called the Theseia from him. But he sheared only the fore part of his head, just as Homer¹ said the Abantes did, and this kind of tonsure was called Theseis after him. [2]

Now the Abantes were the first to cut their hair in this manner, not under instruction from the Arabians, as some suppose, nor yet in emulation of the Mysians, but because they were war-like men and close fighters, who had learned beyond all other men to force their way into close quarters with their enemies. Archilochus is witness to this in the following words:— [3]

Not many bows indeed will be stretched tight, nor frequent slings
Be whirled, when Ares joins men in the moil of war
Upon the plain, but swords will do their mournful work;
For this is the warfare wherein those men are expert
Who lord it over Euboea and are famous with the spear.

² [4] Therefore, in order that they might not give their enemies a hold by their hair, they cut it off. And Alexander of Macedon doubtless understood this when, as they say, he ordered his generals to have the beards of their Macedonians shaved, since these afforded the readiest hold in battle.