Why would God have to die to save people from Himself? Because there is no other way to save anyone from their sins.
Because God is holy and righteous, He must punish anyone who breaks His law. Since He is the one who administers the punishment, we then need to be saved from His righteous judgment. But, since we are not capable of pleasing God by our mere works, the only one left who can cleanse us is God Himself
The one offended is the one who must pardon. If I offend you, I do not ask forgiveness from your neighbor. I have to ask you. The same goes with God. If we sin against Him we have to go to Him to be forgiven. But, simply asking for forgiveness isn't enough. The reason is because when we sin, we sin against a holy and infinite God. But, God is also righteous and He must do what is right. Therefore, it is right to punish those who defy Him. But the problem is that since God is infinite and we are not, we cannot do enough to please an infinite God.
Let's say I am at your house or apartment with my wife. We are talking about church and in my zeal I accidentally knock over your lamp. Now, this lamp is special. A dear friend gave it to you and it has great sentimental value, and besides, you need a light in your room. After a moment or two you realize that the damage is done and decide to forgive. You say to me, "That is alright, Matt. I forgive you for breaking the lamp, but give me ten dollars."
Is asking for ten dollars after you've just forgiven me, true forgiveness? Certainly not! When God forgives our sins, He says He will remember them no more (Jer. 31:34). Forgive and forget are similar in spelling and similar in meaning. If you forgive me can you demand payment from the one forgiven? No, because a forgiven debt does not exist.
Let's say that instead of asking me for ten dollars you turn to my wife and say, "Matt broke my lamp. You give me ten dollars for it."
I ask you again. Is that true forgiveness? No. You are simply transferring the debt to someone who was not involved in the original offense.
But, we have a problem. The lamp needs to be replaced. In true forgiveness, then, who pays for its replacement? (Think about this a bit before you go on to read the answer.) Who pays? You do! You're the only one left. Remember, if you've forgiven me the debt, how can you demand payment?
Now, who was my offense against? You. Who forgives? You do. Who pays? You do.
When we sin, who do we sin against? God. Who forgives? God. Who pays? God! Did you get that? God pays! How does He do that? Simple. 2000 years ago on a hill outside the city of Jerusalem He bore our sins in His body and died on the cross (1 Pet. 2:24). He took our punishment: "Surely our griefs He Himself bore, and our sorrows He carried... He was pierced through for our transgressions, He was crushed for our iniquities; the chastening for our well-being fell upon Him..." (Isaiah 53:4-5).
God is just. God is merciful. God is gracious. In the justice of God, He took our place. In the mercy of God we don't get punished. In the grace of God, He gives us eternal life.
Even though we are unworthy of salvation, even though we are unworthy of God's love, even though we are unworthy of mercy, even though we are worthy of wrath, God saved us. He did so not because of who we are, but because of who He is, not because of what we do, but because of what He did. God is love (1 John 4:16). God is holy (1 Peter 1:16). God is good (Psalm 34:8). We could never fathom the depths of His purity and kindness (Rom. 11:33). We could never, through our own efforts, attain Him. There is only one thing left for us. We must worship Him, love Him, and serve Him. He alone is worthy. Blessed be the name of the Lord.