How do we know that Christ's redemption is sufficient?

In Isaiah 55, the concept of redemption is depicted as a purchase made without money, indicating it is a priceless gift offered by God. This highlights the sufficiency of Christ's redemption, as it was not based on any currency or merit on our part. The notion that Christ not only paid the price for our sins but also offers it freely signifies a grace that cannot be earned. The Apostle Paul emphasizes this in 1 Timothy 1:9, stating that salvation is according to His purpose and grace, inherently reliant on Christ's work rather than our own efforts. Therefore, the assurance of redemption rests firmly on the complete and effective work of Christ on the cross.