Question: "What does it mean that Jesus is our mediator?"
Answer: A mediator is one who mediates, who acts as an intermediary or go-between, to work with opposing sides in order to bring about a settlement. A mediator attempts to influence a disagreement between two parties with the goal of resolving a dispute. There is only one Mediator between mankind and God and that is Jesus Christ. We’ll see below why God has a dispute with us, why Jesus is our mediator, and why we are doomed if we try to “go it alone.”
God has a dispute with us because of sin. Sin is described in the Bible as transgression of the law of God (1 John 3:4) and rebellion against God (Deuteronomy 9:7; Joshua 1:18). God hates sin, and sin stands between all of us and Him. “There is no one righteous, not even one” (Romans 3:10). All human beings are sinners by virtue of sin we have inherited from Adam, as well as the sin we commit on a daily basis. The only just penalty for this sin is death (Romans 6:23), not just physical death but eternal death (Revelation 20:11–15). The rightful punishment for sin is an eternity in hell.
Nothing we could do on our own would be sufficient to mediate between ourselves and God. No amount of good works or law-keeping makes us righteous enough to stand before a holy God (Isaiah 64:6; Romans 3:20; Galatians 2:16). Without a mediator, we are destined to spend eternity in hell, for by ourselves salvation from our sin is impossible. But there is hope! “For there is one God and one mediator between God and men, the man Christ Jesus” (1 Timothy 2:5). Jesus represents those who have placed their trust in Him before God’s throne of grace. He mediates for us, much as a defense attorney mediates for his client, telling the judge, “Your honor, my client is innocent of all charges against him.” That is true for us also, as some day we will face God, but as totally forgiven sinners because of Jesus’ death on our behalf. The “Defense Attorney” took the penalty for us!
We see more comforting proof of this truth in Hebrews 9:15: “For this reason Christ is the mediator of a new covenant, that those who are called may receive the promised eternal inheritance – now that He has died as a ransom to set them free from the sins committed under the first covenant.” It is because of the great Mediator that we are able to stand before God clothed in the righteousness of Christ Himself because on the cross He exchanged our sin for His righteousness (2 Corinthians 5:21). His mediation is the only means of salvation.