Lee WThe most famous riddle there is, and outside Thebes a wrong answer got you eaten.
What walks on four legs in the morning, two legs at noon and three legs in the evening?
Think of a whole life as one day.
A baby crawls on all fours, a grown man walks on two legs, and an old man walks with a stick.
Oedipus got it. The Sphinx threw herself off her rock, and Oedipus took the throne of Thebes and married its widowed queen, who turned out to be his mother.
Source: Apollodorus, Bibliotheca 3.5.8, 1st or 2nd century AD