According to the legend found in Plutarch’s Lives and other sources, when Lycurgus became confident in his reforms, he announced that he would go to the oracle at Delphi to sacrifice to Apollo. However, before leaving for Delphi he called an assembly of the people of Sparta and made everyone, including the kings and Gerousia, take an oath binding them to observe his laws until he returned. He made the journey to Delphi and consulted the oracle, which told him that his laws were excellent and would make his people famous. He then disappeared from history. One explanation was that being satisfied by this he starved himself to death instead of returning home, forcing the citizens of Sparta by oath to keep his laws indefinitely.
Source: Lycurgus of Sparta – Wikipedia