This is one of several descriptions of Spartan values as perceived by other Greeks, many of whom were both attracted and repelled by them. It is taken from Xenophon's The Constitution of the Lacedaemonians. Xenophon lived 444-357 BCE.

In other Greek cities, parents who profess to give their sons the best education place their boys under the care and control of a moral tutor as soon as they can understand what is said to them, and send them to a school to learn letters, music, and the exercises of the wrestling ground. Moreover, they soften the children's feet by giving them sandals, and pamper their bodies with changes of clothing; and it is customary to allow them as much food as they can eat.

Lycurgus, on the contrary, instead of leaving each father to appoint a slave to act as tutor, gave the duty of controlling the boys to a member of the class from which the highest offices are filled, in fact to the "Warden" as he is called. He gave this person authority to punish them severely in case of misconduct. He also assigned to him a staff of youths provided with whips to chastise them when necessary.... [I]nstead of softening their feet with sandals he required them to harden their feet by going without shoes. He believed that if this habit were cultivated it would enable them to climb hills more easily and descend steep slopes with less danger. [A]nd instead of letting them be pampered in the matter of clothing, he introduced the custom of wearing one garment throughout the year, believing that they would thus be better prepared to face changes of heat and cold. As to the food, he required the prefect to bring with him such a moderate amount of it that the boys would never suffer from repletion and would know what it was to go with their hunger unsatisfied; for he believed that those who underwent this training would be better able to continue working on an empty stomach if necessary, and would be capable of carrying on longer without extra food....

[H]e allowed them to alleviate their hunger by stealing something. It was not on account of a difficulty in providing for them that he encouraged them to get their food by cunning.... [O]bviously, a man who intends to take to thieving must spend sleepless nights and play the deceiver and lie in ambush by day, and moreover, if he means to make a capture, he must have spies ready. There can be no doubt then, that all this education was planned by him in order to make the boys more resourceful in getting supplies and be better fighting men.

Xenophon. "The constitution of the Lacedemonians." in Scripta Minora. Loeb ClassicaI Library Cambridge, MA Harvard university Press, 1925.