How do we know Jesus came to save His people from their sins?

Matthew 1:21 clearly articulates the mission of Jesus: 'for he shall save his people from their sins.' This statement underlines the purpose of His coming, affirming that He was born to die as the substitute for His people. The necessity of His sacrificial death is rooted in the doctrine of original sin, where all humanity is born dead in trespasses and sins, needing a Savior to atone for their transgressions. Jesus fulfills this role perfectly, being the spotless Lamb of God who takes away the sin of the world.