How do we know that God's grace is necessary for salvation?

The necessity of God's grace for salvation is clear in the Scriptures, particularly in Ephesians 2:8-9, which says, 'For by grace are ye saved through faith; and that not of yourselves: it is the gift of God: Not of works, lest any man should boast.' This underscores that salvation is not based on human effort but solely on God's unmerited favor towards us. Moreover, Paul in 1 Corinthians 15 highlights that what he is, is entirely by the grace of God, reflecting that grace precedes any action on our part. Salvation is thus rooted in God's initiative and love toward us, showing that it is only through His grace that we can be reconciled to Him.