How do we know that Jesus' work was sufficient for salvation?

We can know that Jesus' work was sufficient for salvation through the promises found in Scripture. Isaiah 53:11 states that the servant of the Lord shall see the travail of His soul and be satisfied. This indicates that the work of Christ, who bore our iniquities, effectively justifies those for whom He died. Moreover, in John 6:39, Jesus assures us that He will lose none of those the Father has given Him. Therefore, the completeness of Christ's atonement is linked directly to the assurance we receive as believers. His sacrifice was not uncertain; rather, it was a definitive act that accomplishes salvation for all those whom God has chosen.