How do we know that Jesus's work on the cross is sufficient for salvation?

The sufficiency of Christ's work on the cross is encapsulated in His proclamation, 'It is finished' (John 19:30). This statement indicates that all requirements for reconciliation with God were met through His sacrifice. In John 17:4, Jesus prayed, 'I have finished the work which You have given Me to do,' establishing that His work of salvation is complete and sufficient for those whom the Father has given to Him. Additionally, Philippians 1:6 reassures us that God will complete the work He has begun in His people, reinforcing the assurance that salvation through Christ is not only sufficient but also final.