Christianity is the only faith that teaches that heaven is a free gift. The Bible says, “the gift of God is eternal life through Jesus Christ our Lord” (Romans 6:23).
Imagine someone gave you a Rolex watch as a gift. If you decided to offer that person $20 for giving you such an expensive gift, what would that watch no longer be? It would no longer be a gift. You just got a great deal on a Rolex watch! The same is true with heaven. We can't earn it. No amount of personal effort, good works, or religious deeds can earn a place in heaven for you.
The Bible says, “For by grace are ye saved through faith; and that not of yourselves: it is the gift of God: not of works, lest any man should boast” (Ephesians 2:8-9).