How do we know that salvation is conditioned entirely on Christ?

The essence of the gospel is that salvation is not conditioned on our works but solely on the completed work of Christ. Ephesians 2:8-9 emphasizes that we are saved by grace through faith, which itself is a gift from God. This reinforces the idea that our faith and salvation do not stem from our efforts but from the grace of God. Furthermore, salvation’s certainty lies in Christ's obedience, life, and sacrificial death, which are imputed to us for justification. Therefore, any doctrine suggesting that human actions or decisions play a role in salvation undermines the grace of God and the sufficiency of Christ's work.