What is the significance of Jesus saying "It is finished" on the cross?

from the old testament

• When Adam and Eve sinned, it started something that would forever change the course of human history and God's work within it. Yet, God began the work of restoring humanity immediately after Adam and Eve sinned. Genesis 3:15 presents the protoevangelium: the first promise that evil would ultimately be defeated through the woman's offspring. Although Satan would wound the promised offspring, the offspring would ultimately crush the serpent's head. This was fulfilled through Christ's death and resurrection.
• After Adam and Eve sinned, God provided garments of skin for them—a provision that covered humanity's sin and shame (Genesis 3:21). God continued to provide substitutes for His people. Genesis 22 provides an important picture of substitutionary sacrifice. When God commanded Abraham to offer Isaac, God provided a ram in his place.
  
• In Exodus 12, God provided the Passover lamb as a substitute, and its blood brought deliverance from judgment. This anticipated Jesus as the ultimate Passover Lamb whose blood would bring deliverance from sin (see John 1:29; 1 Corinthians 5:7).
• Leviticus established the sacrificial system as God's provision for dealing with the guilt and consequences of sin. The repeated sacrifices, particularly the Day of Atonement in Leviticus 16, pointed toward the need for a final sacrifice capable of dealing with sin permanently. Leviticus 17:11 also explains that God gave blood to make atonement for His people. This provides the Old Testament foundation for the New Testament's emphasis on Jesus' blood as the means of redemption and forgiveness.
• Isaiah 52–53 describes a Suffering Servant who would be rejected, wounded, pierced, and crushed because of others' sins. The Servant would bear the iniquities of many, would become a guilt offering, and would make the unrighteous righteous, providing one of the clearest Old Testament pictures of Jesus' sacrificial death. Psalm 22, Psalm 31, Psalm 34, and Psalm 69 also describe aspects of the suffering and death of God's righteous servant, fulfilled in Jesus' crucifixion. These passages demonstrate that Jesus' suffering and death fit the biblical pattern God had already revealed in the Old Testament.

from the new testament

• God's plan of redemption, which began in the Old Testament, found its completion in the New Testament. Jesus repeatedly said that He came to accomplish the work the Father had given Him. John 4:34 says He came to accomplish God's work, and John 17:4 says He had accomplished the work the Father gave Him; therefore, when Jesus says “It is finished” in John 19:30, He declares that His earthly mission had reached its intended goal.
• Jesus' death was not an unexpected defeat but the fulfillment of God's redemptive plan. Acts 2:23 says Jesus was delivered up according to God's definite plan and foreknowledge. Thus, when Jesus said, "It is finished," He meant that He had accomplished God's plan that began back in Genesis 3.
• Jesus' death accomplished what the Old Testament sacrifices could not permanently accomplish. Jesus could say, "It is finished," because He fulfilled the Old Testament sacrificial system. He is the Lamb of God (John 1:29), the Passover Lamb (1 Corinthians 5:7), and the once-for-all sacrifice who bore our sin and provided eternal redemption (Hebrews 9:26–28; 10:10–14).
• Romans 3:23–26, 2 Corinthians 5:21, Galatians 3:13, 1 Peter 2:24, and 1 Peter 3:18 describe Christ's death as the means by which God deals with sin and reconciles sinners to God. Jesus' death fulfilled the Old Testament picture of the Suffering Servant who bore the iniquities of many. He finished what Isaiah 53 prophesied.
• Jesus saying, "It is finished," showed that He had fulfilled the Old Covenant and inaugurated the New Covenant promised by Jeremiah. At the Last Supper, Jesus identified His blood as the blood of the New Covenant (Luke 22:20), and Hebrews identified Him as its mediator (Hebrews 9:15; 12:24), opening direct access to God.
• Because of Christ's finished work, all who trust in Him can receive forgiveness, justification, redemption, and reconciliation with God. Romans 5:1–11, Ephesians 1:7, Colossians 1:19–22, and 2 Corinthians 5:18–21 all describe the restored relationship with God made possible through Christ's death. Through Jesus, the enmity between God and us could be eradicated. In this sense, Jesus' "It is finished" rings true in His decisive victory over the powers of evil, sin, and death.
• At the same time, “It is finished” does not mean that God's entire plan of redemption has reached its final historical conclusion because the resurrection, ascension, sending of the Spirit, gospel mission, and future restoration still follow. Rather, Jesus had completed the decisive sacrificial work necessary for redemption, which the resurrection then vindicates and confirms. The finished work of the cross looks forward to the day when it reaches its final fulfillment, described in Revelation 21–22.

implications for today

Life rarely lets us feel finished. Something always remains to accomplish, improve, fix, prove, or achieve. We can carry that same mindset into our relationship with God, feeling as though we need to pray more, do more, be better, or make up for our failures before we can feel close to Him. But Jesus' words, “It is finished,” confront that way of thinking. The cross reminds us that our relationship with God does not begin with what we do for Him; it begins with what He has already done for us through Christ. We don't have to spend our lives trying to pay a debt Jesus already paid or earn acceptance He has already made possible.

So, we don't have to keep proving ourselves to God once we have trusted in Him for the forgiveness of sins. Instead, we are free to live for Him. When we fail, we don't have to live trapped in shame as though our worst moment has the final word. When we succeed, we don't have to build our identity around our accomplishments as though they make us more valuable to God. Instead, we can confess what needs to be confessed, receive God's grace, get back up, and keep following Christ.

“It is finished” does not mean there is nothing left for us to do; it means we are no longer working for God's acceptance but living from the acceptance Christ secured. We can stop striving to prove that we are enough and start living with the confidence that, because of Jesus, we belong to God. The cross frees us to stop trying to finish what Jesus already finished and start faithfully living out what He has made possible.