Why is faith in Christ alone necessary for salvation?

The necessity of faith in Christ alone for salvation stems from the concept of justification, which is the act of being declared righteous before God. This is not achieved through our works or righteousness but through the imputed righteousness of Christ. As indicated in 2 Corinthians 5:21, Christ became sin for us so that in Him we might become the righteousness of God. By placing our faith solely in Christ's finished work, we acknowledge our inability to save ourselves and accept the gift of grace that leads to salvation. This faith is what unites us to Christ and secures our place before the Father, assuring us of His promises.