If people in Egypt had an unanswered question they would go to the sphinx. The Spinx would tell them their answer but only if they answered the following riddle : What has 4 legs in the morning, two legs during the day, and three legs at night?" What is the answer
The answer is man, because:
In the 'morning'of his life (i.e. as a baby) he goes on four legs (crawls). In the 'day' he goes on two legs. At 'night' (i.e. when elderly) he goes on three legs - one of the legs being a stick.
The sphinx was at Thebes, a city in central Greece, not in Egypt. Word didn't get round about the riddle as the sphinx would kill anyone who failed to answer it. No-one could answer it until Oedipus cracked it and slew the sphinx.