The assurance lies in the Scriptures, which affirm that Christ's sacrifice fully satisfies God's justice for His elect.
The assurance of Christ having drunk the cup for us stems from the covenantal promises found in Scripture. In Romans 10:9, it says, 'That if thou shalt confess with thy mouth the Lord Jesus, and shalt believe in thy heart that God hath raised him from the dead, thou shalt be saved.' This assurance is grounded in His perfect obedience and satisfaction of God’s justice. The reality that God accepted Christ's sacrifice as sufficient for our sins is further supported by the resurrection, which signifies that the debt is completely paid. Thus, for those who believe, the promise is clear: Christ’s sacrifice was for His people.
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