Why do Christians believe in substitutionary atonement?

Substitutionary atonement is a core tenet of Christian faith since it explains how Christ's death reconciled us to God. As highlighted in Psalm 85 and throughout Scripture, God's justice requires that the penalty of sin must be paid. Jesus, as our substitute, bore the full weight of our sin, allowing God's justice to be satisfied while extending His grace to the elect. This doctrine affirms that redemption is solely by Christ's sacrifice, providing a means for God to be both just and merciful, which is the essence of the gospel's glory.