How do we know that salvation depends entirely on God's grace?

The assertion that salvation relies entirely on God's grace is firmly rooted in scriptural doctrine. Titus 3:5-6 highlights this: 'Not by works of righteousness which we have done, but according to His mercy He saved us, through the washing of regeneration and renewing of the Holy Spirit, whom He poured out on us abundantly through Jesus Christ our Savior.' This passage distinguishes between human righteousness and divine mercy, emphasizing that it is God's initiative that predicates salvation. Moreover, the doctrine aligns with foundational Reformed theology which asserts that since all have sinned and fall short of the glory of God (Romans 3:23), salvation could not possibly arise from human actions or decisions. The emphasis on grace reinforces the understanding of God's redemptive plan as something bestowed upon the undeserving, celebrating His immense mercy and love.