How do we know that God is just in punishing Christ?

God's justice is an essential aspect of His character, as seen in Psalm 22 where the Savior's suffering reflects the necessity of divine justice. The Father forsook the Son because Christ was made sin for His people, bearing the weight of their transgressions. This act demonstrates that God cannot look upon sin without executing justice, even when it resides in His beloved Son. Thus, the punishment of Christ was not an injustice; rather, it was the fulfillment of God's holy nature, allowing Him to uphold justice while extending mercy to sinners. This complexity is at the heart of the Gospel, showing how justice and grace work together through salvation in Christ.