The phrase "slow and steady wins the race," comes from the internationally recognised Aesop's Fable "The Tortoise and the Hare." It is a story of two unequal partners who have a race. The story is used to illustrate that consistency and perseverance outweigh speed.
In the story a hare challenges a tortoise to a race having criticised the tortoise for being too slow. The tortoise accepts the challenge. At first the hare races ahead but is so confident, he decides to take a rest and falls asleep. The tortoise focuses on the finish line and never stops going as fast as he can. The hare awakes to see him cross the finish line.