Salvation must be God's gift since it cannot be worked for or earned as a result of people's efforts. Something that is earned can no longer be a gift, it is wages. God's grace caused Him to send Jesus to die on the cross for people's sin. Jesus' death on the cross was the demonstration of God's grace. This death of Christ on the cross was a free gift since there was no one who deserved being died for.
Salvation is offered to people as a gift.
Those who try to earn the gift will fall short because of their sin. Only those who are willing to reach out by faith will take hold of the free gift of salvation. There is no room for boasting in salvation because salvation is not earned or deserved. A person could boast or brag about his salvation if sal-vation came as a result of works or effort. But the Christian message is humbling, indeed.