A selection of verses showing that we cannot earn salvation, it is given freely by God.
Jesus makes it clear that eternal life is a gift from a loving God:
16 For God so loved the world, that he gave his one and only Son, that whoever believes in him should not perish, but have eternal life.
Paul tells us that death is a result of our sins, but by grace we can receive the gift of eternal life though Jesus:
15 But the free gift isn’t like the trespass. For if by the trespass of the one the many died, much more did the grace of God, and the gift by the grace of the one man, Jesus Christ, abound to the many.
23 For the wages of sin is death, but the free gift of God is eternal life in Christ Jesus our Lord.
Ultimately it is faith that leads to eternal life:
22 But the Scripture imprisoned all things under sin, that the promise by faith in Jesus Christ might be given to those who believe.