How do we know Jesus fulfilled His purpose?

In John 17:4, Jesus declares, 'I have glorified Thee on the earth.' This assertion reflects His confidence that He has completed the work the Father sent Him to accomplish. By fulfilling the law and offering Himself as a perfect sacrifice, Jesus secured salvation for all whom the Father had given Him. His resurrection further confirms this fulfillment, showcasing that God’s promises are sure and that Jesus is victorious in His mediatorial role. If He had failed in this task, it would mean that God's purpose could be thwarted, which contradicts the essence of God’s sovereign nature.