Some Muslim critics of Christianity attack the power of the Christian God by stating that he is too weak to forgive a person's sins without the shedding of blood. These critics often say that if the Christian God is so powerful, then why can't he declare a person to be forgiven without requiring a blood sacrifice? They sometimes view this as a weakness in the Christian concept of God. But this is not a weakness. It is a declaration of the holiness of the God of Christianity and the lack of holiness of the God of Islam.
In Christianity, God is far too holy to accept the sincerity and repentance of a person so as to forgive that person of his or her sins. But in Islam, a person's sincerity and repentance are sufficient to warrant forgiveness - if Allah so grants it. Why the difference? The difference is due to the fact that God has revealed in the Bible that his Holiness is so complete and so perfect, and that our sinfulness is so pervasive, that even our sincerity and our repentance are touched by sin and are not acceptable to him. Because sin has touched all of what we are: our hearts, our minds, our intentions, our wills, our emotions, etc, our efforts just can't be good enough. For a Muslim to say that God can forgive a person because the person is sincere is to say that his own heart is good enough to earn a place with God. In other words, he is appealing to the sincerity of his own heart, and this amounts to pride. It is pride because it is based on the person's self-worth, self-ability, and goodness of heart. Islam teaches that a person can be good enough to please God--if he does enough good works and sincerely repents of his sin. By contrast, the view of Christianity is that because of God's infinite holiness and man's sinfulness, the gap between them cannot be bridged by our own efforts, our own sincerity, our own works, or even our own repentance. None of these are sufficient to please an infinitely holy and perfect God. But, they are enough for the God of Islam.
In Christianity God provides for us the very forgiveness that our sincerity and repentance cannot bring. If our salvation, if the forgiveness of our sins could come by anything that we do, then Jesus did not need to die on the cross (Gal. 2:21). But it was necessary that Jesus, who was God in flesh and second person of the Trinity, provide for us what we could not accomplish. Only in Christianity is the infinite love of God manifested so completely that he humbles himself and loves us so much that he took our place of punishment to ensure salvation. This is good news for the Christian. But, the Muslim has no such good news. He is stuck with the uncertain hope that maybe, just maybe, his own sincerity and repentance might be good enough to warrant forgiveness from his God.
Therefore, we conclude that the God of Islam is not holy because he accepts the sin-touched repentance and sin-touched sincerity of Muslims for the forgiveness of their sins.
By contrast, the God of Christianity is too holy for that. He requires holiness because he is holy (1 Pet. 1:16). But the God of Islam does not require holiness. Instead, the God of Islam accepts the Muslim's sin-stained works and sin-stained repentance.
Only in Christianity does God himself provide what sinful man cannot accomplish. In Christ, God cleanses us of our sins by HIS work (on the cross) and not by sinful man's sincerity or sinful man's repentance. The God of the Bible does it all because of his great holiness. The God of Islam does not because he is not holy.
Into which system do you wish to place your hopes: in Christianity where God provides and guarantees salvation or in Islam where Allah does not?