The phrase "seeing His offspring and prolonging His days" is found in the prophetic book of Isaiah, specifically in Isaiah 53:10. This passage is part of the "Suffering Servant" prophecy, which is a profound and pivotal text in the Old Testament, often interpreted by Christians as a messianic prophecy foretelling the life, death, and resurrection of Jesus Christ.

Isaiah 53:10 :
"Yet it was the LORD’s will to crush Him and cause Him to suffer. And when His soul is made a guilt offering, He will see His offspring, He will prolong His days, and the will of the LORD will prosper in His hand."

Context and Interpretation:

1. The Suffering Servant: Isaiah 53 is a part of the larger section of Isaiah known as the "Servant Songs" (Isaiah 42-53), which describe a servant of the Lord who will bring justice and salvation. Isaiah 53, in particular, details the suffering, rejection, and ultimate vindication of this servant. Christians traditionally interpret this servant as Jesus Christ, who fulfills these prophecies through His life, death, and resurrection.

2. Seeing His Offspring: The phrase "He will see His offspring" is understood in a spiritual sense. In the New Testament, believers in Christ are often referred to as children of God (John 1:12, Romans 8:16-17). Thus, the "offspring" of the Suffering Servant are those who come to faith in Christ, becoming part of the family of God. This interpretation aligns with the idea that through His sacrificial death, Jesus brings many to salvation, creating a spiritual lineage.

3. Prolonging His Days: The phrase "He will prolong His days" is seen as a reference to the resurrection of Jesus. Although He was crucified and died, Christians believe that Jesus rose from the dead on the third day, conquering death and living eternally. This resurrection is seen as the ultimate vindication of the Suffering Servant, affirming His divine nature and the fulfillment of God's redemptive plan.

4. The Will of the LORD: The latter part of Isaiah 53:10, "the will of the LORD will prosper in His hand," indicates that the suffering and subsequent exaltation of the Servant are part of God's sovereign plan. Through the Servant's obedience and sacrifice, God's purposes are accomplished, bringing salvation to humanity and establishing His kingdom.

Theological Significance:

The prophecy in Isaiah 53:10 holds deep theological significance for Christians. It encapsulates the core of the Gospel message: that through the suffering and resurrection of Jesus Christ, believers are brought into a new covenant relationship with God. The imagery of "offspring" and "prolonging days" speaks to the eternal impact of Christ's work, ensuring the continuation of His mission through the lives of His followers and His eternal reign.

This passage also highlights the paradox of the cross—where apparent defeat becomes victory, and death leads to life. It underscores the belief in a God who brings redemption out of suffering and life out of death, a central tenet of Christian faith.