Muslims often ask why it is necessary for God to die for man's sins. Why can't we just confess our sins and have God forgive us? Isn't that enough? Following is an attempt to logically demonstrate the necessity of God atoning for our sins.
God is infinite. There is no limit to Him. He is endless.
God is holy. Holiness is purity. God is incapable of doing anything wrong. Part of the quality of holiness is the inability to do wrong.
God is just. He always does what is right. God cannot violate His own righteousness declarations, because that would mean God is contradicting Himself. This justice is according to His nature since it is He is who tells us what is right and wrong.
Therefore, God is infinitely holy and infinitely just. Neither His holiness nor justice can be denied since they are part of His character and God cannot be denied.
We are not infinite and not holy. We are not infinite because we are creations. We are not holy because we have sinned.
Sin is doing anything against God's Law. It is God who declares what is right and wrong. He has revealed this to us in the scriptures.
The Law is a reflection of God's character. God speaks out of what is in His mind and heart. If He says do not lie, it is because it is against God's nature to lie. God is not speaking without reason or purpose. If He had no reason or purpose, this would mean that God is not trustworthy. God is trustworthy, therefore God's Law is the standard of perfection, justice, and holiness.
God's Law carries a penalty upon the sinner which is damnation. Damnation is the act of God where He passes righteous judgment upon a person because of the person's sin against Him. If breaking God's law did not carry a penalty, then there would be no damnation. But since there is damnation, we can conclude that breaking God's law carries a penalty. If He did not damn based upon righteousness, then God is doing wrong. Since God cannot do anything wrong, then damnation is righteous.
God is affected by what we do. Proof of this is found in our prayers. Since God answers our prayers, our prayers have an affect upon God because God is moved to answer. If our prayers have no affect upon God, then prayer is useless since it accomplishes nothing.
Breaking God's Law, sinning, has a negative effect upon our relationship with God. God is not injured in a physical way by our sins since God is spirit, perfect, and complete. But, since damnation exists (because of the justice of God), we can conclude that sin has a negative affect upon the relationship between the sinner and God. If this were not so, there would be no damnation.
Since God is infinite, our offense against Him has an infinite effect. It is the infinite God we have offended, therefore, the sin results in an infinite offense against God.
A finite person cannot remove an infinite offense against an infinite God. A finite work cannot remove an infinite offense because the effort of a finite person will always fall short of meeting the justice of an infinite God.
God cannot arbitrarily forgive the sinner without satisfying His infinite justice. If damnation is righteously given because of justice, so too, forgiveness must be in accordance with justice because both are dealing with sin. To simply dismiss sin in order to forgive is to deny justice. If forgiveness is not consistent with God's justice, then God is arbitrary, inconsistent, and unjust. Therefore, the act of forgiveness also requires an act of justice.
Since it is just that the sinner die and be damned, this justice cannot be ignored. If it were ignored, then God is not being consistent in His justice. If it were ignored, then God has no right to damn anyone. No one is damned who is alive. Only the dead are damned.
Since man cannot earn forgiveness from God through his finite works, it must be God who makes forgiveness possible. This is so, because there is no one left to make things right, other than God.
Since it is not just to ignore the penalty for sin, and since man cannot satisfy God, there is none left but God to pay for the just penalty of sin. The sin cannot be ignored because the act of forgiveness also requires and act of justice. This justice cannot be ignored because God would then be inconsistent.
It is just that the sinner die and suffer judgment. Death is a punishment of God and damnation follows death.
Since it is just that sin must be dealt with, God must meet that requirement of justice. This is so, because a finite person cannot please and infinite God's just requirements of holiness and purity. God must then do what is just in forgiveness of sins or justice cannot be met.
God must then take the place of the sinner and suffer the consequence of the lawful judgment of death upon the sinner.
With justice met, forgiveness can then be rightly given.
This forgiveness, which cannot be earned by man's effort, can only be received from God by man's faith - because there is nothing else he can do.