John 6:29 KJV
Jesus answered and said unto them, This is the work of God, that ye believe on him whom he hath sent.
John 6:47 KJV
Verily, verily, I say unto you, He that believeth on me hath everlasting life.
The work is believing. It is the only work and it is the only thing needful for salvation.
But because of the corruption of the flesh it is not possible to believe except the Father gives us the faith and except God the Father draws us.
The saddest thing in the world is that many who are drawn never come. Faith is what saves and that faith is a gift from God. But some who are offered this gift reject it.
• The fear of man
• The pride of life or
• The love of the world
lead them to accept cheaper thrills instead. And we can't have the cheaper thrills and the heavenly rewards too.
It is one or the other.