.....First let's look at the source of the shield story, which isn't Herodotus but the Roman writer Plutarch. He writes, "Another woman handed her son his shield, and exhorted him: 'Son, either with this or on this.'" This quote is found in Plutarch's Moralia, a collection of morals, tales, and short stories, in a section called Sayings of Spartan Women.
Plutarch was a Greek, born approximately 46 AD in the town of Chaeronea in the region of Boeotia. He isn't a contemporary source of the saying, as the days of Spartan military glory had ended more than three centuries earlier. As a modern commentator observes, he could have been taking poetic license:
At the beginning of his Life of Alexander … Plutarch says, explicitly, that his purpose is not to write political history, but to bring out the subjects' particular virtues and vices and to illustrate his character. This purpose is worth bearing in mind — Plutarch's lives are not necessarily objective historical accounts, but narrative pictures aiming to convey a particular moral point.
In his work Plutarch consistently portrays the Spartans as having a tough, no-nonsense warrior culture, a characterization backed up by other Greek writers, including contemporaries of Sparta in its glory.....