What is the riddle given by the sphinx?

The riddle given by the Sphinx is: "What walks on four legs in the morning, two legs at noon, and three legs in the evening?" The answer is "a human." In the morning of life (infancy), a person crawls on all fours; during adulthood (noon), they walk on two legs; and in old age (evening), they often use a cane, thus walking on three legs.